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Investigation of Chinese text entry performance for mobile display interfaces Po-Hung Lin
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Department of Industrial Engineering & Management Information, Huafan University, New Taipei City 223, Taiwan Published online: 26 Sep 2014.
Click for updates To cite this article: Po-Hung Lin (2015) Investigation of Chinese text entry performance for mobile display interfaces, Ergonomics, 58:1, 107-117, DOI: 10.1080/00140139.2014.961565 To link to this article: http://dx.doi.org/10.1080/00140139.2014.961565
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Ergonomics, 2015 Vol. 58, No. 1, 107–117, http://dx.doi.org/10.1080/00140139.2014.961565
Investigation of Chinese text entry performance for mobile display interfaces Po-Hung Lin* Department of Industrial Engineering & Management Information, Huafan University, New Taipei City 223, Taiwan (Received 25 August 2013; accepted 20 August 2014)
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This study examined the effects of panel type, frequency of use and arrangement of phonetic symbols on operation time, usability, visual fatigue and workload in text entry performance. Three types of panel (solid, touch and mixed), three types of frequency of use (low, medium and high) and two types of the arrangement of phonetic symbols (vertical and horizontal) were investigated through 30 college students in the experiment. The results indicated that panel type, frequency of use, arrangement of phonetic symbols and the interaction between panel type and frequency of use were significant factors on operation time. Panel type was also a significant factor on usability, and a touch panel and a solid panel showed better usability than a mixed panel. Furthermore, a touch panel showed good usability and the lowest workload and therefore it is recommended to use a touch panel with vertical phonetic arrangement in sending Chinese text messages. Practitioner Summary: This study found, from ergonomics considerations, that a touch panel showed good usability and it is recommended to use a touch panel with vertical phonetic arrangement in sending Chinese text messages. Mobile display manufacturers can use the results of this study as a reference for future keyboard design. Keywords: mobile display; text entry performance; panel type; frequency of use; arrangement of phonetic symbols
1. Introduction With the promotion of technology, information needs have increased greatly. As a result, many types of electronic products have been invented to fulfil these needs. Given their convenience and portability, electronic products such as personal digital assistants (PDAs) and mobile displays have been widely used. In addition to oral communication functions, mobile phones offer another alternative for sending messages. Compared to phone conversation, text messaging provides some advantages such as silent communication, less time consuming and sending a message to a large number of people at a time (Peslak, Ceccucci, and Sendall 2010), and has become a popular form of communication, especially for young people. Therefore, the interface for sending the text messages in mobile phones is worthy to be investigated. Due to the advance of technology, the touch panel has become one of the most popular interfaces in the market. Touch screen incorporates hardware and software interfaces in a touchable panel that can detect the presence and location of a touch within the display area. It is a kind of friendly and lively creation in human –machine interfaces that can be applied widely in tools such as PDAs, navigation devices, tablet PCs, automatic teller machines (ATMs) and others public facilities. Compared to other input devices, Shneidemnan (1991) indicated that the advantages of a touch screen are that it is easy to learn, is easier for hand – eye coordination than mice or keyboards, requires no extra space and is durable in public-access and high-volume usage. However, some problems have been identified, including screen obscuration, lower position and tilting to result in arm fatigue, brightness reduction and higher cost (Shneidemnan 1991). In text entry tasks, Wright et al. (2000) indicated that physical keyboards showed the better accuracy and speed than touch screens. Varcholik, LaViola, and Hughes (2012) further indicated that the text entry efficiency and speed of touch panels are inferior to physical keyboards. Nevertheless, due to its convenience, the touch panel has become the mainstream in the market. Sears (1991) pointed out that even though using speech for text entry with a touch panel is not as fast as using the traditional panel, it still offers alternatives. Recent studies had also investigated the text entry performance on touch screens (Rudchenko, Paek, and Badge 2011; Malik and Findlater 2013). All of the above literatures were based on English text entry tasks. However, the text entry tasks used in this study are sending Chinese text messages. Past studies had investigated the Chinese text entry performance for different input methods (Lin and Sears 2005, 2007). Nevertheless, the study examining the difference between touch panels and physical keyboards under single input method (like phonetic-based method used in this study) in Chinese text entry tasks is quite few. Except for touch panels and physical keyboards, a mixed panel which is composed of a touch panel and a physical keyboard simultaneously was the third panel considered in this study. Based on above arguments, it is worthy to investigate the performance among panel types in Chinese text entry tasks.
*Email: [email protected] q 2014 Taylor & Francis
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Table 1.
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The mobile displays used in the experiment.
Panel type Touch panel
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Mixed panel
Solid panel
Vertical
Horizontal
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Many studies have investigated the effect of keyboard layout (Mackenzie, Zhang, and Soukoreff 1999; MacKenzie and Zhang 2001; Sears et al. 2001). Mackenzie, Zhang, and Soukoreff (1999) investigated the text entry rates using six keyboard layouts, including the QWERTY, FITALY, Alphabetic, Dvorak, JustType and Telephone. Although Dvorak (1943) and Griffith (1949) proposed other kinds of keyboard layouts to improve efficiency, the QWERTY layout remains one of the most popular layouts in the market. Meanwhile, the telephone keyboard layout is currently the most used layout for mobile displays. In the telephone keyboard, phone numbers are composed of 12 keys, including the numbers 0 through 9 and 3 function keys. Due to the lack of the space, many English alphabets and Chinese phonetic symbols are placed on each key. Mackenzie, Zhang, and Soukoreff (1999) indicated that the data entry rate using the telephone keyboard is inferior to the rate using the QWERTY keyboard. However, the advantage of the telephone keyboard is that it is easy to manipulate due to its small size; thus, the text entry task for the telephone keyboard is worth investigating (Mackenzie, Zhang, and Soukoreff 1999). Although the telephone keyboard is frequently used in most mobile displays, the QWERTY keyboard is also used in mobile displays, such as the vertical mixed panel used in this experiment. Therefore, the QWERTY keyboard and telephone keyboard were the two keyboards investigated in this study. In the market, phonetic symbols on the telephone keyboard have been divided into vertical and horizontal arrangements among different brands (see Table 1). However, research investigating the effect of arrangement on phonetic symbols is quite limited. Past similar studies had investigated the difference between vertical and horizontal arrangements of text (Coleman and Kim 1961; Coleman and Hahn 1966). Laarni (2002) and Laarni et al. (2004) further investigated the difference between vertical and horizontal arrangements of text on PDAs and computer screens, respectively. Based on the conclusions of these studies, the performance of reading vertical text is not always inferior to that of the horizontal format, and the vertical arrangement seems to be a viable alternative. Therefore, the differences between vertical and horizontal layouts of phonetic symbols are worth to be examined. User experience is a person’s perceptions and responses that result from the use or anticipated use of a product, system or service (ISO 2010). Chamorro-Koc, Popovic, and Emmison (2009) identified the relationships among human experience, knowledge and context-of-use, and showed that the feature with indication of usage is one of the subcategories including in human experience. O’Brien et al. (2008) mentioned that a wide range of system users using the system at different frequency levels (e.g. occasional vs. frequent use) and concluded that usage is affected by practice. Some studies had investigated the effect of frequency of use in text messaging tasks (Peslak, Ceccucci, and Sendall 2010; Peslak, Ceccucci, and Bhatnagar 2012). In addition, people who use a product by different frequency could be seemed as having different user experience. Mackenzie, Zhang, and Soukoreff (1999) showed that the entry rates among novices (7 – 10 words per minute [wpm]), experienced users (21 wpm) and experts (43 wpm) differed. Zhai, Hunter, and Smith (2002) further emphasised on performance optimisation of keyboard for novices. Compared to expert experience, MacKenzie and Soukoreff (2002) also indicated that novice experience is the most important for the consumer market. Based on above arguments, participants used to sending the text messages through mobile devices might have high user experience from high frequency of use, resulting in high text entry performance. Therefore, different frequency of use may have different impacts on text entry tasks and it is investigated in this study. In summary, panel type, frequency of use and the arrangement of phonetic symbols are three critical factors affecting people when sending Chinese text messages. The purpose of this study is to assess the effects of these three factors on the operation time, usability, visual fatigue and workload. 2. 2.1.
Method Experimental design
Three independent variables were evaluated in this study: panel type, frequency of use and the arrangement of phonetic symbols. The three panel types are touch panel, mixed panel (phonetic symbols selection using the solid panel; words selection, deletion and confirmation using the touch panel) and solid panel (see Table 1). High, medium and low frequency of use was based on participants’ text entry times of more than 15, between 15 and 5, and fewer than 5 times a week, respectively. The arrangement of phonetic symbols is classified into vertical and horizontal arrangements. Therefore, there were 3 (panel type) £ 3 (frequency of use) £ 2 (the arrangement of phonetic symbols) combinations. A mixed factorial design was conducted where frequency of use and phonetic arrangement served as between-subject factors and panel type served as a within-subject factor. 2.2.
Participants
A total of 30 college students (ages: mean ¼ 22.9 years old, standard deviation ¼ 1.8 years old) took part in this experiment. All had corrected visual acuity better than 0.8.
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For the classification of participants, two questions were asked before the experiment. The first question is ‘Have you ever send a text message through a mobile phone?’ If the participants answered YES, then the second question is ‘How many times do you send the text message in a week? and why?’ We chose the 30 participants who have the experience of sending messages. A participant without any experience in text messaging is prohibited since his/her performance may have the huge difference comparing to others. Then, the three groups were classified according to their frequency of use within a week. According to the summary of times, about one-third of participants reported that they send the text messages more than 15 times a week, and also one-third of them reported less than 5 times a week. Therefore, high, medium and low user frequency of use was based on participants’ text entry times of more than 15, between 15 and 5, and fewer than 5 times a week, respectively. A total of 30 participants were randomly assigned to each of the three groups. Each participant completed the three different types of panels under one of the combinations of frequency of use and the arrangement of phonetic symbols in the experiment.
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2.3.
Apparatus
A TOPCON ACP7 vision tester and Standard Pseudo Isochromatic charts were used to test participants’ visual acuity and colour vision. The critical fusion frequency (CFF) value was measured with a LAFAYETTE 12021 Flicker Fusion. The six mobile displays were HTC Legend (320 £ 480 pixels, 112 £ 56.3 £ 11.5 mm), iPhone 4G (960 £ 640 pixels, 115.2 £ 58.6 £ 9.3 mm), LG GW620 (320 £ 480 pixels, 109 £ 54.5 £ 15.9 mm), Nokia C3-01 (240 £ 320 pixels, 111 £ 47.5 £ 11 mm), Moto VE 538 (240 £ 320 pixels, 107 £ 46 £ 15 mm) and Nokia N73 (240 £ 320 pixels, 110 £ 49 £ 19 mm), as shown according to phonetic arrangement and panel type in Table 1. 2.4. Condition of workplace The experimental task arrangement is shown in Figure 1. The mobile display was positioned on a table with 73 cm in height. The front edge of the table was 20 cm from the display centre. The inclination angle of the mobile display was 1058 for the vertical axis (Turville et al. 1998). The viewing distance was 25 cm and the participant’s head was restrained by a chinrest 15 cm above the table. Before conducting the experiment, the height of seat could be adjusted by the participants to make them comfortable. 2.5. Task and procedure A paragraph of Chinese text entry task was used to evaluate operation time, usability, visual fatigue and workload. Of the 500 highest frequency used Chinese characters, 70 were selected (Ministry of Education of Taiwan website http://www.edu. tw/pages/list.aspx?Node¼ 3691&Index ¼ 7&wid ¼ c5ad5187-55ef-4811-8219-e946fe04f725, accessed August 22, 2013). The pseudo-text was randomly composed of 63 Chinese characters and 7 Chinese punctuation marks. These Chinese
Figure 1.
The arrangement of the workspace in the experiment.
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characters were 18-point font size of New Thin Ming type. The configuration of pseudo-text was arranged in 7 lines per page, with 10 characters per line. Figure 2 shows the pseudo-text in Chinese used in this experiment. Each participant had to finish the three different types of panels under one of the combinations of frequency of use and the arrangement of phonetic symbols. The procedure of the experiment was as follows:
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(1) The visual acuity of the participant was obtained from the vision tester. If the score was lower than 0.8, the participant was not allowed to join in the experiment. (2) The CFF threshold of a participant was reported twice before each treatment. The first time, the CFF value was adjusted from high frequency to low frequency and the second time from low to high. The CFF threshold was the average of these two values. (3) The participant adjusted the seat and placed his or her head on the fixed chinrest to keep the 50- cm viewing distance. (4) The participant was asked to type the Chinese characters from left to right, from up to down. The operation time was recorded after the participant completed each treatment. (5) As in Step (2), the CFF threshold was obtained after each treatment. Then, the participant was asked to evaluate usability and workload through the questionnaire. (6) A 10-minute break was given between treatments, and the procedure continued until participants finished the three treatments. 2.6.
Dependent measures and data analysis
Four dependent measures were analysed: operation time, usability, change of CFF and workload. Operation time was defined as the total time for typing the Chinese characters and punctuation marks. Usability was defined as the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use (ISO 1988). In this study, a system usability scale (SUS) questionnaire, found by Brooke (1996), was used to investigate users’ usability of mobile displays. Participants’ visual fatigue was measured by the change of CFF, which was the difference between the CFF thresholds before and after treatments. For workload, the NASA task load index (NASA-TLX) proposed by Hart and Staveland (1998) was used to measure the subjective workload. This commonly used rating scale is based on six independent scales: mental demand, physical demand, temporal demand, performance, effort and frustration. We conducted the analysis of variance (ANOVA) with repeated measures on operation time, usability, change of CFF and workload. The Duncan multiple range test was used to find the significances among the levels of independent variables. All statistical analyses were calculated with the Statistical Products Services Solution. 3.
Results
The mean proportion of operation time, usability, change of CFF and workload at each level of the independent variables is shown in Table 2. The ANOVA results for each dependent variable are shown below.
Figure 2.
A paragraph of the Chinese pseudo-text used in the experiment.
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Table 2.
Mean operation time, usability, change of CFF and workload at each level of the independent variables.
Independent variables Panel type Touch panel Mixed panel Solid panel Frequency of use High Middle Low Phonetic arrangement Vertical Horizontal
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3.1.
n
Operation time (second)
Usability
Change of CFF (Hz)
Workload
30 30 30
540.4 555.5 478.4
64.13 49.76 65.35
2 1.05 2 0.56 2 0.56
48.33 55.56 53.71
10 10 10
434.2 522.5 617.6
57.47 59.33 62.45
0.00 2 0.93 2 1.85
51.96 55.58 50.06
15 15
492 544.9
60.06 59.44
2 0.07 2 1.37
48.56 56.51
Operation time
The ANOVA results for operation time are shown in Table 3, which indicates that panel type (F(2, 48) ¼ 5.052, p , 0.05), frequency of use (F(2, 24) ¼ 32.954, p , 0.01), phonetic arrangement (F(1, 24) ¼ 4.694, p , 0.05) and panel £ phonetic arrangement (F(2, 48) ¼ 6.099, p , 0.05) were the significant factors. The significant interaction between panel and phonetic arrangement (P £ PA) was needed to test the simple main effect within the interaction. Therefore, we focused on each panel, investigating its effect on arrangement of phonetic symbols. As shown in Figure 3, these results revealed that, with the mixed panel ( p . 0.05) and solid panel ( p . 0.05), the differences between vertical and horizontal arrangements were not significant, whereas the differences were significant with the touch panel ( p , 0.01). The mean values of operation time for vertical and horizontal arrangements are 469.3 and 612 seconds, respectively. We then studied the effect of each arrangement of phonetic symbols on panel type. For horizontal arrangement, the differences among panel types were significant ( p , 0.05). Therefore, it is essential to conduct the Duncan test for different panels. The results indicated that the only significant difference was between the touch panel and solid panel ( p , 0.05), and the mean value of operation time is better in the solid panel (464.9 seconds) than in the touch panel (611.4 seconds). For vertical arrangement, the differences among panel types were not significant. Except for the panel and phonetic arrangement interaction, the ANOVA results also indicated that frequency of use was a significant factor (F(2, 24) ¼ 32.954, p , 0.01). The operation time decreased as frequency of use level increased. The results were further analysed by the Duncan test, revealing that operation time on frequency of use was high . medium . low, which means that the three levels of frequency of use were significantly different from one another. In addition, panel type was also significant on operation time (F(2, 48) ¼ 5.052, p , 0.05). The mean values of operation time for touch panel, mixed panel and solid panel were 540.4, 555.5 and 478.4 seconds, respectively. The results of the Duncan test demonstrated that significant differences between touch panel and solid panel ( p , 0.05) and between mixed panel and solid panel ( p , 0.05) were found. Moreover, the phonetic arrangement was also significant on operation time (F (1, 24) ¼ 4.694, p , 0.05). The mean values of operation time for vertical and horizontal arrangements were 492 and 544 seconds, respectively.
Table 3.
ANOVA results of dependent variables.
Source Within subject Panel (P) P*F P*PA P*F*PA Between subject Frequency of use (F) Phonetic arrangement (PA) F*PA *p , 0.05; **p , 0.01.
Operation time
Usability
Change of CFF
Workload
5.052* 1.023 6.099* 1.603
5.2* 1.867 4.082 0.593
0.55 1.401 3.586 1.569
2.097 2.393 2.15 1.512
32.954** 4.694* 2.164
0.523 0.079 0.34
0.375 1.96 1.773
0.612 3.685 0.125
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Figure 3.
3.2.
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The interaction between panel type and arrangement of phonetic symbols on operation time.
Usability
The results of the SUS score for usability are shown in Table 3, and the main effect plot is shown in Figure 4. It indicated that panel type (F(2, 48) ¼ 5.2, p , 0.05) was the significant factor. The mean values of SUS score for touch panel, mixed panel and solid panel were 64.13, 49.76 and 64.75, respectively. The results of the Duncan test demonstrated that significant differences were found between the mixed panel and the touch panel ( p , 0.05), and between the mixed panel and the solid panel ( p , 0.05).
Figure 4.
The SUS score as a function of panel type.
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3.3. Change of CFF and workload The ANOVA results for change of CFF and workload indicated that none of the independent variables were significant. 4.
Discussion
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Based on the experimental results, operation time, usability, change of CFF and workload issues were discussed as follows. 4.1. Operation time The results indicated that panel type (F ¼ 5.052, p , 0.05) and arrangement of phonetic symbols (F ¼ 4.694, p , 0.05) were significant on operation time. However, an interaction between panel type and arrangement of phonetic was also found (F ¼ 6.099, p , 0.05). For panel type, the results showed that the arrangement of phonetic symbols was significant only for the touch panel, and the operation performance of the vertical arrangement was significantly better than that of the horizontal one. The result is in accord with the study of Laarni (2002), which indicated that the reading speed and comprehension of vertical text were slightly better than horizontal text due to the decrease of participants’ horizontal eye movements. In addition, Sears et al. (2001) and MacKenzie and Zhang (2001) demonstrated that participants’ best performance occurred while using a familiar keyboard. Hunnius and Geuze (2004) found that the users’ operation performance is affected by their past cognition. In this study, the vertical arrangement on the touch panel is similar to the QWERTY layout. As most participants have experience with document processing using the QWERTY layout, a better operation time was expected with vertical arrangement. Except for the touch panel, the results indicated that solid and mixed panels were not significant on the arrangement of phonetic symbols. For the solid panel, as both horizontal and vertical arrangements use the telephone layout with more than three symbols on each key, the similar operation time seems reasonable. With regard to the mixed panel, although the vertical arrangement is similar to the QWERTY layout, due to lack of enough keys to represent all symbols, the composite keys (e.g. the two enlarged composite keys on the far right of the QWERTY keyboard in Table 1) are used and switched according to colour. Participants had to spend more time and pay more attention searching for the symbols; therefore, insignificance was found between horizontal and vertical arrangements. For the effect of each arrangement of phonetic symbols on panel type, the results showed that panel type was significant only for the horizontal arrangement, while the operation performance of the solid panel was significantly better than that of the touch panel, which was also shown in main factor effect of panel type. The results are in accord with the study of Wright et al. (2000), which indicated significant decrements in accuracy and speed when entering text via the touch screen. Furthermore, the results are in accord with the study of Varcholik, LaViola, and Hughes (2012), which indicated that the physical keyboard outperformed the multi-touch monitor in the text entry task. The text entry devices used in Varcholik, LaViola, and Hughes (2012) were a physical keyboard and a 22-inch touch monitor, whereas the text entry devices used in this study were hand-held keypads and approximately 4-inch touch screens. As the physical keyboard outperformed the touch monitor in the study of Varcholik, LaViola, and Hughes (2012), it might be more reasonable in this study for the solid panel to demonstrate better performance than the touch and mixed ones because small text entry devices can easily lead to participants’ typing mistakes. However, the results might be inconsistent with the state-of-the-art market trend as the solid panel seems less popular among users than the touch panel in the phone market. One possible reason for the results is that this experiment was conducted in 2010, when solid panels were still popular. Participants also reported that they are more familiar with solid panels than mixed and touch ones. Second, participants were reported that they sometimes touched the keys but received no response or even touched the wrong keys when using touch or mixed panels. In addition to issues of unfamiliarity, the activation area in selected touch panels might not correspond to the finger touch point, resulting in no response. It is compatible with the argument of Wright et al. (2000) that one of the drawbacks of touch screens was the lack of tactile Table 4.
The measurement of key size of mobile displays.
Panel type
Mobile phone
L (cm)
W (cm)
Square measure (cm2)
Touch Touch Mixed Mixed Solid Solid
HTC legend iPhone 4G LG GW620 Nokia C3-01 Moto VE538 Nokia N73
0.4 1.1 0.85 1.4 1.2 1
0.6 0.5 0.5 0.7 0.5 0.5
0.24 0.55 0.425 0.98 0.6 0.5
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feedback. Third, unlike solid panels, the text entry task in touch panels needs precise activation on its keys. When key size is small, the key size could be covered by the fingers and result in the wrong keys being activated, thereby lengthening the operation time. Wright et al. (2000) also indicated that one of the problems for small touch screens is key size. Kwon, Lee, and Chung (2009) further set key size as an independent variable and indicated that user performance and preference were improved as the key size increased. As shown in Table 4, the square measurements of key size in HTC legend and iPhone 4G were the first smallest and almost third smallest in all panels. Since the key size of touch panels in this study is relatively small, it may be a possible explanation for the result. Forth, participants reported that the design with one symbol on one key of the touch panel increases the time (including the time for typing mistakes) compared to the design with many symbols on one key of the solid panel; therefore, the overall operation time was extended. Finally, participants were not allowed to use handwriting input function of the touch panel, which might further explain the results. The results also indicated that the frequency of use was significant on operation time (F ¼ 32.954, p , 0.01), demonstrating that the higher the frequency of use, the better the operation performance. The results were in line with those of Forlizzi and Battarbee (2004), who showed that users’ individual experience affects the performance evaluation. Mackenzie, Zhang, and Soukoreff (1999) also indicated that different performances of entry rates occurred among novices, experts and experienced users. Peslak, Ceccucci, and Sendall (2010) further indicated that frequency of use was influenced between young and elder people in text messaging tasks. 4.2. Usability The results indicated that panel type was a significant factor on usability. The results further showed that the usability with the touch and solid panels was significantly better than with the mixed panel. Regardless of whether dealing with vertical or horizontal arrangements of the mixed panel, participants had to seek phonetic symbols of the composite key on the keyboard and then select the word on the touch screen. The shift in hand positioning from the keyboard to the touch screen could result in low usability and long operation time. The results also indicated that no significant difference was found between the touch panel and solid panel. Bangor, Kortum, and Miller (2008) indicated that the mean SUS scores above 52.01 represented an appropriate usability of a product. In this study, the SUS scores of the solid and touch panels were 65.35 and 64.13, respectively. The advantages of the solid panel are its simplicity and consistency. In addition, the selection key and the direction key were in the same area, making it easier for participants to manipulate. For the touch panel, as the simulated keypad appears directly on the screen, except for the one symbol on each key enhancing clarity and ease, participants were not affected by the mapping of the physical keypad. The results of this study concur with the results of Albinsson and Zhai (2003), which pointed out that the touch panel was considered to be participants’ primary user interface with a wider screen and higher flexibility. Therefore, both the touch and solid panels have good usability for sending Chinese text messages. 4.3.
Change of CFF and workload
Panel type, frequency of use and arrangement of phonetic symbols were not significant on change of CFF and workload. A possible reason, also the limitation of this study, was that the operation time is below 10 minutes. Although Iwasaki, Kurimot, and Noro (1989) indicated that the red colour CFF is significantly decreasing after working for 15 minutes with CRT display screens, the screens of mobile displays used in this study were only 2 –4 inches and therefore it is considered that smaller screens could result in more visual fatigue easily. That is why the text entry task was set in the experiment. From the results of this study, it can be inferred that future studies for text entry performance should be conducted with more visual loadings and longer operation time so that the performance of visual fatigue and workload might be significant. Although insignificances were found, we further explained the results from the means. As shown in Table 2, the mean of change of CFF decreased as frequency of use increased and this trend was also found in operation time and usability. This implies that participants with high frequency of use might perform better performance in Chinese text entry tasks. In addition, the mean of change of CFF decreased as the phonetic arrangement moved from horizontal to vertical; this trend was also found in operation time and workload, implying that vertical arrangement might provide a better performance for Chinese text entry tasks. 4.4.
Comparison between operation time and usability
As shown in the results, the operation time of the solid panel is significantly better than that of the touch panel. However, insignificance for usability was found between them. With the growing popularity of the touch panel in the future, users will get used to manipulating the touch panel and therefore the operation time with the touch panel is expected to decrease.
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Although a high operation performance of the touch panel was not obtained, good usability was achieved in this study. Similarly, the performance of the vertical arrangement was significantly better than that of the horizontal arrangement. However, insignificance for usability was found between them. It indicated that participants consider that the horizontal arrangement is also an alternative for usability. This result was in accord with Laarni et al. (2004), which indicated that reading horizontally may be nearly as efficient as reading vertically. Besides, the possible reason for low operation performance could be that participants were not familiar with the horizontal arrangement.
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5.
Conclusion
The main contribution of this study was to explore the effects of panel type, frequency of use and arrangement of phonetic symbols on operation time, usability, change of CFF and workload for Chinese text entry performance. The results indicated that panel type, frequency of use, arrangement of phonetic symbols and the interaction between panel type and frequency of use were significant factors on operation time. The results also demonstrated that the solid panel, high frequency of use and vertical phonetic arrangement provide the best operation performance. In addition, the touch and solid panels showed better usability than the mixed panel. The touch panel showed good usability and the lowest workload in sending Chinese text messages. Since solid panels will be replaced by touch panels in the future and the future design of touch panels should provide people with more advanced and convenient interfaces with high usability, we recommend that people use the touch panel with vertical phonetic arrangement in sending Chinese text messages. Future studies could be conducted to include a text entry task with additional paragraphs of Chinese to investigate the impact on participants’ performance after a prolonged task. In addition, participants reported that they sometimes touched the keys but received no response or even touched the wrong keys when using touch or mixed panels. Therefore, future studies should explore the contact angle and area between the finger and the touch keys as well as the setup of the touch key contact points. References Albinsson, P. A., and S. Zhai. 2003. “High Precision Touch Screen Interaction.” In The CHI 2003 Conference on Human Factors in Computing Systems, edited by Cockton, Gilbert and Korhonen Panu, 105– 112. New York: ACM Press. Bangor, Aaron, Philip T. Kortum, and James T. Miller. 2008. “An Empirical Evaluation of the System Usability Scale.” International Journal of Human-Computer Interaction 24 (6): 574– 594. Brooke. 1996. “SUS: A ‘Quick and Dirty’ Usability Scale.” In Usability Evaluation in Industry, edited by P. W. Jordan, B. Thomas, B. A. Weerdmeester, and I. L. McClelland, 189– 194. London: Taylor & Francis. Chamorro-Koc, Marianella, Vesna Popovic, and Michael Emmison. 2009. “Human Experience and Product Usability: Principles to Assist the Designof User – Product Interactions.” Applied Ergonomics 40: 648– 656. Coleman, E. B., and S. C. Hahn. 1966. “Failure to Improve Readability with a Vertical Typography.” Journal of Applied Psychology 50: 434– 436. Coleman, E. B., and I. Kim. 1961. “Comparison of Several Styles of Typography in English.” Journal of Applied Psychology 45: 262– 267. Dvorak, A. 1943. “There is a Better Typewriter Keyboard.” National Business Education Quarterly 12: 51 – 58. Forlizzi, J., and K. Battarbee. 2004. “Understanding Experience in Interactive Systems.” In The 5th Conference on Designing Interactive Systems, 261– 268. New York: ACM Press. Griffith, R. T. 1949. “The Minimotion Typewriter Keyboard.” Journal of the Franklin Institute 248: 399–436. Hart, S. G., and L. Staveland. 1998. Development of NASA-TLX (Task Load Index): Results of Empirical and Theoretical Research. Amsterdam: Elsevier. Hunnius, S., and R. H. Geuze. 2004. “Developmental Changes in Visual Scanning of Dynamic Faces and Abstract Stimuli in Infants: A Longitudinal Study.” Infancy 6 (2): 231– 255. doi:10.1207/s15327078in0602_5 ISO. 1988. “ISO9241: Ergonomic Requirements for Office Work with Visual Display Terminals (VDTs) – Part 11: Guidance on Usability.” Internation Organization for Standardization. ISO. 2010. “ISO9241-210: Ergonomics of Human System Interaction – Part 210: Human-Centered Design for Interactive Systems.” International Organization for Standardization. Iwasaki, T., S. Kurimot, and K. Noro. 1989. “The Change in Colour Flicker Fusion (CFF) Values and Accommodaction Time during Experimental Repetitive Tasks with CRT Display Screens.” Ergonomics 32 (3): 293– 305. Kwon, Sunghyuk, Donghun Lee, and Min K. Chung. 2009. “Effect of Key Size and Activation Area on the Performance of a Regional Error Correction Method in a Touch-Screen QWERTY Keyboard.” International Journal of Industrial Ergonomics 39: 888– 893. Laarni, J. 2002. “Searching for Optimal Methods of Presenting Dynamic Text on Different Types of Screens.” In The Second Nordic ˚ rhus: ACM Conference on Human-Computer Interaction, edited by Bertelsen, Olav W. Bodker, Susanne and Kuutti Kari, 217– 220. A Press. Laarni, J., J. Simola, I. Kojo, and N. Risto. 2004. “Reading Vertical Text from a Computer Screen.” Behaviour and Information Technology 23 (2): 75 – 82. Lin, M., and A. Sears. 2005. “Chinese Character Entry for Mobile Phones: A Longitudinal Investigation.” Interacting with Computers 17 (2): 121– 146. doi:10.1016/j.intcom.2004.11.003
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Lin, Min, and Andrew Sears. 2007. “Constructing Chinese Characters: Keypad Design for Mobile Phones.” Behaviour & Information Technology 26 (2): 165– 178. MacKenzie, I., and R. Soukoreff. 2002. “Text Entry for Mobile Computing: Models and Methods,Theory and Practice.” HumanComputer Interaction 17: 147– 198. MacKenzie, I. S., and S. X. Zhang. 2001. “An Empirical Investigation of the Novice Experience with Soft Keyboards.” Behaviour & Information Technology 20 (6): 411– 418. doi:10.1080/01449290110089561 Mackenzie, I. Scott, Shawn X. Zhang, and R. William Soukoreff. 1999. “Text Entry Using Soft Keyboards.” Behaviour and Information Technology 18 (4): 235– 244. Malik, Sana, and Leah Findlater. 2013. Punctuation Input on Touchscreen Keyboards: Analyzing Frequency of Use and Mode-Switching Costs. College Park: The Human-Computer Interaction Lab, University of Maryland. O’Brien, M. A., W. A. Rogers, A. D. Fisk, and M. Richman. 2008. “Assessing Design Features of Virtual Keyboards for Text Entry.” Human Factors 50 (4): 680– 698. doi:10.1518/001872008x312279 Peslak, Alan, Wendy Ceccucci, and Neelima Bhatnagar. 2012. “Analysis of the Variables that Affect Fequency of Use and Time Spent on Text Messaging.” Issues in Information Systems 13 (1): 361– 370. Peslak, Alan R., Wendy Ceccucci, and Patricia Sendall. 2010. “An Empirical Study of Text Messaging Behavioral Intention and Usage.” Journal of Information Systems Applied Research 3 (3): 1 – 19. Rudchenko, Dmitry, Tim Paek, and Eric Badge. 2011. “Text Text Revolution: A Game that Improves Text Entry on Mobile Touchscreen Keyboards.” Paper presented at the 9th international conference on pervasive computing, San Francisco, CA, USA. Sears, A. 1991. “Improving Touchscreen Keyboards: Design Issues and a Comparison with Other Devices.” Interacting with Computers 3: 253– 269. Sears, A., J. A. Jacko, J. Chu, and F. Moro. 2001. “The Role of Visual Search in the Design of Effective Soft Keyboards.” Behaviour & Information Technology 20 (3): 159– 166. doi:10.1080/01449290110049790 Shneidemnan, Ben. 1991. “Touch Screens Now Offer Compelling Uses.” IEEE Software, 93 – 94. Turville, K. L., J. P. Psihogios, T. R. Ulmer, and G. A. Mirka. 1998. “The Effect of Video Display Terminal Height on the Operator: A Comparison of 15 and 40 Recommendations.” Applied Ergonomics 29: 239– 246. Varcholik, P. D., J. J. LaViola, and C. E. Hughes. 2012. “Establishing a Baseline for Text Entry for a Multi-Touch Virtual Keyboard.” International Journal of Human-Computer Studies 70 (10): 657– 672. doi:10.1016/j.ijhcs.2012.05.007 Wright, Patricia, Christine Bartam, Nick Rogers, Hazel Emslie, Jonathan Evans, Barbara Wilson, and Steve Belt. 2000. “Text Entry on Handheld Computers by Older Users.” Ergonomics 43 (6): 702–716. Zhai, Shumin, Michael Hunter, and Barton A. Smith. 2002. “Performance Optimization of Virtual Keyboards.” Human-Computer Interaction 17: 229– 269.
Ergonomics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/terg20
Investigation of Chinese text entry performance for mobile display interfaces Po-Hung Lin
a
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Department of Industrial Engineering & Management Information, Huafan University, New Taipei City 223, Taiwan Published online: 26 Sep 2014.
Click for updates To cite this article: Po-Hung Lin (2015) Investigation of Chinese text entry performance for mobile display interfaces, Ergonomics, 58:1, 107-117, DOI: 10.1080/00140139.2014.961565 To link to this article: http://dx.doi.org/10.1080/00140139.2014.961565
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Ergonomics, 2015 Vol. 58, No. 1, 107–117, http://dx.doi.org/10.1080/00140139.2014.961565
Investigation of Chinese text entry performance for mobile display interfaces Po-Hung Lin* Department of Industrial Engineering & Management Information, Huafan University, New Taipei City 223, Taiwan (Received 25 August 2013; accepted 20 August 2014)
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This study examined the effects of panel type, frequency of use and arrangement of phonetic symbols on operation time, usability, visual fatigue and workload in text entry performance. Three types of panel (solid, touch and mixed), three types of frequency of use (low, medium and high) and two types of the arrangement of phonetic symbols (vertical and horizontal) were investigated through 30 college students in the experiment. The results indicated that panel type, frequency of use, arrangement of phonetic symbols and the interaction between panel type and frequency of use were significant factors on operation time. Panel type was also a significant factor on usability, and a touch panel and a solid panel showed better usability than a mixed panel. Furthermore, a touch panel showed good usability and the lowest workload and therefore it is recommended to use a touch panel with vertical phonetic arrangement in sending Chinese text messages. Practitioner Summary: This study found, from ergonomics considerations, that a touch panel showed good usability and it is recommended to use a touch panel with vertical phonetic arrangement in sending Chinese text messages. Mobile display manufacturers can use the results of this study as a reference for future keyboard design. Keywords: mobile display; text entry performance; panel type; frequency of use; arrangement of phonetic symbols
1. Introduction With the promotion of technology, information needs have increased greatly. As a result, many types of electronic products have been invented to fulfil these needs. Given their convenience and portability, electronic products such as personal digital assistants (PDAs) and mobile displays have been widely used. In addition to oral communication functions, mobile phones offer another alternative for sending messages. Compared to phone conversation, text messaging provides some advantages such as silent communication, less time consuming and sending a message to a large number of people at a time (Peslak, Ceccucci, and Sendall 2010), and has become a popular form of communication, especially for young people. Therefore, the interface for sending the text messages in mobile phones is worthy to be investigated. Due to the advance of technology, the touch panel has become one of the most popular interfaces in the market. Touch screen incorporates hardware and software interfaces in a touchable panel that can detect the presence and location of a touch within the display area. It is a kind of friendly and lively creation in human –machine interfaces that can be applied widely in tools such as PDAs, navigation devices, tablet PCs, automatic teller machines (ATMs) and others public facilities. Compared to other input devices, Shneidemnan (1991) indicated that the advantages of a touch screen are that it is easy to learn, is easier for hand – eye coordination than mice or keyboards, requires no extra space and is durable in public-access and high-volume usage. However, some problems have been identified, including screen obscuration, lower position and tilting to result in arm fatigue, brightness reduction and higher cost (Shneidemnan 1991). In text entry tasks, Wright et al. (2000) indicated that physical keyboards showed the better accuracy and speed than touch screens. Varcholik, LaViola, and Hughes (2012) further indicated that the text entry efficiency and speed of touch panels are inferior to physical keyboards. Nevertheless, due to its convenience, the touch panel has become the mainstream in the market. Sears (1991) pointed out that even though using speech for text entry with a touch panel is not as fast as using the traditional panel, it still offers alternatives. Recent studies had also investigated the text entry performance on touch screens (Rudchenko, Paek, and Badge 2011; Malik and Findlater 2013). All of the above literatures were based on English text entry tasks. However, the text entry tasks used in this study are sending Chinese text messages. Past studies had investigated the Chinese text entry performance for different input methods (Lin and Sears 2005, 2007). Nevertheless, the study examining the difference between touch panels and physical keyboards under single input method (like phonetic-based method used in this study) in Chinese text entry tasks is quite few. Except for touch panels and physical keyboards, a mixed panel which is composed of a touch panel and a physical keyboard simultaneously was the third panel considered in this study. Based on above arguments, it is worthy to investigate the performance among panel types in Chinese text entry tasks.
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Table 1.
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The mobile displays used in the experiment.
Panel type Touch panel
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Mixed panel
Solid panel
Vertical
Horizontal
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Many studies have investigated the effect of keyboard layout (Mackenzie, Zhang, and Soukoreff 1999; MacKenzie and Zhang 2001; Sears et al. 2001). Mackenzie, Zhang, and Soukoreff (1999) investigated the text entry rates using six keyboard layouts, including the QWERTY, FITALY, Alphabetic, Dvorak, JustType and Telephone. Although Dvorak (1943) and Griffith (1949) proposed other kinds of keyboard layouts to improve efficiency, the QWERTY layout remains one of the most popular layouts in the market. Meanwhile, the telephone keyboard layout is currently the most used layout for mobile displays. In the telephone keyboard, phone numbers are composed of 12 keys, including the numbers 0 through 9 and 3 function keys. Due to the lack of the space, many English alphabets and Chinese phonetic symbols are placed on each key. Mackenzie, Zhang, and Soukoreff (1999) indicated that the data entry rate using the telephone keyboard is inferior to the rate using the QWERTY keyboard. However, the advantage of the telephone keyboard is that it is easy to manipulate due to its small size; thus, the text entry task for the telephone keyboard is worth investigating (Mackenzie, Zhang, and Soukoreff 1999). Although the telephone keyboard is frequently used in most mobile displays, the QWERTY keyboard is also used in mobile displays, such as the vertical mixed panel used in this experiment. Therefore, the QWERTY keyboard and telephone keyboard were the two keyboards investigated in this study. In the market, phonetic symbols on the telephone keyboard have been divided into vertical and horizontal arrangements among different brands (see Table 1). However, research investigating the effect of arrangement on phonetic symbols is quite limited. Past similar studies had investigated the difference between vertical and horizontal arrangements of text (Coleman and Kim 1961; Coleman and Hahn 1966). Laarni (2002) and Laarni et al. (2004) further investigated the difference between vertical and horizontal arrangements of text on PDAs and computer screens, respectively. Based on the conclusions of these studies, the performance of reading vertical text is not always inferior to that of the horizontal format, and the vertical arrangement seems to be a viable alternative. Therefore, the differences between vertical and horizontal layouts of phonetic symbols are worth to be examined. User experience is a person’s perceptions and responses that result from the use or anticipated use of a product, system or service (ISO 2010). Chamorro-Koc, Popovic, and Emmison (2009) identified the relationships among human experience, knowledge and context-of-use, and showed that the feature with indication of usage is one of the subcategories including in human experience. O’Brien et al. (2008) mentioned that a wide range of system users using the system at different frequency levels (e.g. occasional vs. frequent use) and concluded that usage is affected by practice. Some studies had investigated the effect of frequency of use in text messaging tasks (Peslak, Ceccucci, and Sendall 2010; Peslak, Ceccucci, and Bhatnagar 2012). In addition, people who use a product by different frequency could be seemed as having different user experience. Mackenzie, Zhang, and Soukoreff (1999) showed that the entry rates among novices (7 – 10 words per minute [wpm]), experienced users (21 wpm) and experts (43 wpm) differed. Zhai, Hunter, and Smith (2002) further emphasised on performance optimisation of keyboard for novices. Compared to expert experience, MacKenzie and Soukoreff (2002) also indicated that novice experience is the most important for the consumer market. Based on above arguments, participants used to sending the text messages through mobile devices might have high user experience from high frequency of use, resulting in high text entry performance. Therefore, different frequency of use may have different impacts on text entry tasks and it is investigated in this study. In summary, panel type, frequency of use and the arrangement of phonetic symbols are three critical factors affecting people when sending Chinese text messages. The purpose of this study is to assess the effects of these three factors on the operation time, usability, visual fatigue and workload. 2. 2.1.
Method Experimental design
Three independent variables were evaluated in this study: panel type, frequency of use and the arrangement of phonetic symbols. The three panel types are touch panel, mixed panel (phonetic symbols selection using the solid panel; words selection, deletion and confirmation using the touch panel) and solid panel (see Table 1). High, medium and low frequency of use was based on participants’ text entry times of more than 15, between 15 and 5, and fewer than 5 times a week, respectively. The arrangement of phonetic symbols is classified into vertical and horizontal arrangements. Therefore, there were 3 (panel type) £ 3 (frequency of use) £ 2 (the arrangement of phonetic symbols) combinations. A mixed factorial design was conducted where frequency of use and phonetic arrangement served as between-subject factors and panel type served as a within-subject factor. 2.2.
Participants
A total of 30 college students (ages: mean ¼ 22.9 years old, standard deviation ¼ 1.8 years old) took part in this experiment. All had corrected visual acuity better than 0.8.
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For the classification of participants, two questions were asked before the experiment. The first question is ‘Have you ever send a text message through a mobile phone?’ If the participants answered YES, then the second question is ‘How many times do you send the text message in a week? and why?’ We chose the 30 participants who have the experience of sending messages. A participant without any experience in text messaging is prohibited since his/her performance may have the huge difference comparing to others. Then, the three groups were classified according to their frequency of use within a week. According to the summary of times, about one-third of participants reported that they send the text messages more than 15 times a week, and also one-third of them reported less than 5 times a week. Therefore, high, medium and low user frequency of use was based on participants’ text entry times of more than 15, between 15 and 5, and fewer than 5 times a week, respectively. A total of 30 participants were randomly assigned to each of the three groups. Each participant completed the three different types of panels under one of the combinations of frequency of use and the arrangement of phonetic symbols in the experiment.
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2.3.
Apparatus
A TOPCON ACP7 vision tester and Standard Pseudo Isochromatic charts were used to test participants’ visual acuity and colour vision. The critical fusion frequency (CFF) value was measured with a LAFAYETTE 12021 Flicker Fusion. The six mobile displays were HTC Legend (320 £ 480 pixels, 112 £ 56.3 £ 11.5 mm), iPhone 4G (960 £ 640 pixels, 115.2 £ 58.6 £ 9.3 mm), LG GW620 (320 £ 480 pixels, 109 £ 54.5 £ 15.9 mm), Nokia C3-01 (240 £ 320 pixels, 111 £ 47.5 £ 11 mm), Moto VE 538 (240 £ 320 pixels, 107 £ 46 £ 15 mm) and Nokia N73 (240 £ 320 pixels, 110 £ 49 £ 19 mm), as shown according to phonetic arrangement and panel type in Table 1. 2.4. Condition of workplace The experimental task arrangement is shown in Figure 1. The mobile display was positioned on a table with 73 cm in height. The front edge of the table was 20 cm from the display centre. The inclination angle of the mobile display was 1058 for the vertical axis (Turville et al. 1998). The viewing distance was 25 cm and the participant’s head was restrained by a chinrest 15 cm above the table. Before conducting the experiment, the height of seat could be adjusted by the participants to make them comfortable. 2.5. Task and procedure A paragraph of Chinese text entry task was used to evaluate operation time, usability, visual fatigue and workload. Of the 500 highest frequency used Chinese characters, 70 were selected (Ministry of Education of Taiwan website http://www.edu. tw/pages/list.aspx?Node¼ 3691&Index ¼ 7&wid ¼ c5ad5187-55ef-4811-8219-e946fe04f725, accessed August 22, 2013). The pseudo-text was randomly composed of 63 Chinese characters and 7 Chinese punctuation marks. These Chinese
Figure 1.
The arrangement of the workspace in the experiment.
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characters were 18-point font size of New Thin Ming type. The configuration of pseudo-text was arranged in 7 lines per page, with 10 characters per line. Figure 2 shows the pseudo-text in Chinese used in this experiment. Each participant had to finish the three different types of panels under one of the combinations of frequency of use and the arrangement of phonetic symbols. The procedure of the experiment was as follows:
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(1) The visual acuity of the participant was obtained from the vision tester. If the score was lower than 0.8, the participant was not allowed to join in the experiment. (2) The CFF threshold of a participant was reported twice before each treatment. The first time, the CFF value was adjusted from high frequency to low frequency and the second time from low to high. The CFF threshold was the average of these two values. (3) The participant adjusted the seat and placed his or her head on the fixed chinrest to keep the 50- cm viewing distance. (4) The participant was asked to type the Chinese characters from left to right, from up to down. The operation time was recorded after the participant completed each treatment. (5) As in Step (2), the CFF threshold was obtained after each treatment. Then, the participant was asked to evaluate usability and workload through the questionnaire. (6) A 10-minute break was given between treatments, and the procedure continued until participants finished the three treatments. 2.6.
Dependent measures and data analysis
Four dependent measures were analysed: operation time, usability, change of CFF and workload. Operation time was defined as the total time for typing the Chinese characters and punctuation marks. Usability was defined as the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use (ISO 1988). In this study, a system usability scale (SUS) questionnaire, found by Brooke (1996), was used to investigate users’ usability of mobile displays. Participants’ visual fatigue was measured by the change of CFF, which was the difference between the CFF thresholds before and after treatments. For workload, the NASA task load index (NASA-TLX) proposed by Hart and Staveland (1998) was used to measure the subjective workload. This commonly used rating scale is based on six independent scales: mental demand, physical demand, temporal demand, performance, effort and frustration. We conducted the analysis of variance (ANOVA) with repeated measures on operation time, usability, change of CFF and workload. The Duncan multiple range test was used to find the significances among the levels of independent variables. All statistical analyses were calculated with the Statistical Products Services Solution. 3.
Results
The mean proportion of operation time, usability, change of CFF and workload at each level of the independent variables is shown in Table 2. The ANOVA results for each dependent variable are shown below.
Figure 2.
A paragraph of the Chinese pseudo-text used in the experiment.
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Table 2.
Mean operation time, usability, change of CFF and workload at each level of the independent variables.
Independent variables Panel type Touch panel Mixed panel Solid panel Frequency of use High Middle Low Phonetic arrangement Vertical Horizontal
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3.1.
n
Operation time (second)
Usability
Change of CFF (Hz)
Workload
30 30 30
540.4 555.5 478.4
64.13 49.76 65.35
2 1.05 2 0.56 2 0.56
48.33 55.56 53.71
10 10 10
434.2 522.5 617.6
57.47 59.33 62.45
0.00 2 0.93 2 1.85
51.96 55.58 50.06
15 15
492 544.9
60.06 59.44
2 0.07 2 1.37
48.56 56.51
Operation time
The ANOVA results for operation time are shown in Table 3, which indicates that panel type (F(2, 48) ¼ 5.052, p , 0.05), frequency of use (F(2, 24) ¼ 32.954, p , 0.01), phonetic arrangement (F(1, 24) ¼ 4.694, p , 0.05) and panel £ phonetic arrangement (F(2, 48) ¼ 6.099, p , 0.05) were the significant factors. The significant interaction between panel and phonetic arrangement (P £ PA) was needed to test the simple main effect within the interaction. Therefore, we focused on each panel, investigating its effect on arrangement of phonetic symbols. As shown in Figure 3, these results revealed that, with the mixed panel ( p . 0.05) and solid panel ( p . 0.05), the differences between vertical and horizontal arrangements were not significant, whereas the differences were significant with the touch panel ( p , 0.01). The mean values of operation time for vertical and horizontal arrangements are 469.3 and 612 seconds, respectively. We then studied the effect of each arrangement of phonetic symbols on panel type. For horizontal arrangement, the differences among panel types were significant ( p , 0.05). Therefore, it is essential to conduct the Duncan test for different panels. The results indicated that the only significant difference was between the touch panel and solid panel ( p , 0.05), and the mean value of operation time is better in the solid panel (464.9 seconds) than in the touch panel (611.4 seconds). For vertical arrangement, the differences among panel types were not significant. Except for the panel and phonetic arrangement interaction, the ANOVA results also indicated that frequency of use was a significant factor (F(2, 24) ¼ 32.954, p , 0.01). The operation time decreased as frequency of use level increased. The results were further analysed by the Duncan test, revealing that operation time on frequency of use was high . medium . low, which means that the three levels of frequency of use were significantly different from one another. In addition, panel type was also significant on operation time (F(2, 48) ¼ 5.052, p , 0.05). The mean values of operation time for touch panel, mixed panel and solid panel were 540.4, 555.5 and 478.4 seconds, respectively. The results of the Duncan test demonstrated that significant differences between touch panel and solid panel ( p , 0.05) and between mixed panel and solid panel ( p , 0.05) were found. Moreover, the phonetic arrangement was also significant on operation time (F (1, 24) ¼ 4.694, p , 0.05). The mean values of operation time for vertical and horizontal arrangements were 492 and 544 seconds, respectively.
Table 3.
ANOVA results of dependent variables.
Source Within subject Panel (P) P*F P*PA P*F*PA Between subject Frequency of use (F) Phonetic arrangement (PA) F*PA *p , 0.05; **p , 0.01.
Operation time
Usability
Change of CFF
Workload
5.052* 1.023 6.099* 1.603
5.2* 1.867 4.082 0.593
0.55 1.401 3.586 1.569
2.097 2.393 2.15 1.512
32.954** 4.694* 2.164
0.523 0.079 0.34
0.375 1.96 1.773
0.612 3.685 0.125
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Figure 3.
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The interaction between panel type and arrangement of phonetic symbols on operation time.
Usability
The results of the SUS score for usability are shown in Table 3, and the main effect plot is shown in Figure 4. It indicated that panel type (F(2, 48) ¼ 5.2, p , 0.05) was the significant factor. The mean values of SUS score for touch panel, mixed panel and solid panel were 64.13, 49.76 and 64.75, respectively. The results of the Duncan test demonstrated that significant differences were found between the mixed panel and the touch panel ( p , 0.05), and between the mixed panel and the solid panel ( p , 0.05).
Figure 4.
The SUS score as a function of panel type.
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3.3. Change of CFF and workload The ANOVA results for change of CFF and workload indicated that none of the independent variables were significant. 4.
Discussion
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Based on the experimental results, operation time, usability, change of CFF and workload issues were discussed as follows. 4.1. Operation time The results indicated that panel type (F ¼ 5.052, p , 0.05) and arrangement of phonetic symbols (F ¼ 4.694, p , 0.05) were significant on operation time. However, an interaction between panel type and arrangement of phonetic was also found (F ¼ 6.099, p , 0.05). For panel type, the results showed that the arrangement of phonetic symbols was significant only for the touch panel, and the operation performance of the vertical arrangement was significantly better than that of the horizontal one. The result is in accord with the study of Laarni (2002), which indicated that the reading speed and comprehension of vertical text were slightly better than horizontal text due to the decrease of participants’ horizontal eye movements. In addition, Sears et al. (2001) and MacKenzie and Zhang (2001) demonstrated that participants’ best performance occurred while using a familiar keyboard. Hunnius and Geuze (2004) found that the users’ operation performance is affected by their past cognition. In this study, the vertical arrangement on the touch panel is similar to the QWERTY layout. As most participants have experience with document processing using the QWERTY layout, a better operation time was expected with vertical arrangement. Except for the touch panel, the results indicated that solid and mixed panels were not significant on the arrangement of phonetic symbols. For the solid panel, as both horizontal and vertical arrangements use the telephone layout with more than three symbols on each key, the similar operation time seems reasonable. With regard to the mixed panel, although the vertical arrangement is similar to the QWERTY layout, due to lack of enough keys to represent all symbols, the composite keys (e.g. the two enlarged composite keys on the far right of the QWERTY keyboard in Table 1) are used and switched according to colour. Participants had to spend more time and pay more attention searching for the symbols; therefore, insignificance was found between horizontal and vertical arrangements. For the effect of each arrangement of phonetic symbols on panel type, the results showed that panel type was significant only for the horizontal arrangement, while the operation performance of the solid panel was significantly better than that of the touch panel, which was also shown in main factor effect of panel type. The results are in accord with the study of Wright et al. (2000), which indicated significant decrements in accuracy and speed when entering text via the touch screen. Furthermore, the results are in accord with the study of Varcholik, LaViola, and Hughes (2012), which indicated that the physical keyboard outperformed the multi-touch monitor in the text entry task. The text entry devices used in Varcholik, LaViola, and Hughes (2012) were a physical keyboard and a 22-inch touch monitor, whereas the text entry devices used in this study were hand-held keypads and approximately 4-inch touch screens. As the physical keyboard outperformed the touch monitor in the study of Varcholik, LaViola, and Hughes (2012), it might be more reasonable in this study for the solid panel to demonstrate better performance than the touch and mixed ones because small text entry devices can easily lead to participants’ typing mistakes. However, the results might be inconsistent with the state-of-the-art market trend as the solid panel seems less popular among users than the touch panel in the phone market. One possible reason for the results is that this experiment was conducted in 2010, when solid panels were still popular. Participants also reported that they are more familiar with solid panels than mixed and touch ones. Second, participants were reported that they sometimes touched the keys but received no response or even touched the wrong keys when using touch or mixed panels. In addition to issues of unfamiliarity, the activation area in selected touch panels might not correspond to the finger touch point, resulting in no response. It is compatible with the argument of Wright et al. (2000) that one of the drawbacks of touch screens was the lack of tactile Table 4.
The measurement of key size of mobile displays.
Panel type
Mobile phone
L (cm)
W (cm)
Square measure (cm2)
Touch Touch Mixed Mixed Solid Solid
HTC legend iPhone 4G LG GW620 Nokia C3-01 Moto VE538 Nokia N73
0.4 1.1 0.85 1.4 1.2 1
0.6 0.5 0.5 0.7 0.5 0.5
0.24 0.55 0.425 0.98 0.6 0.5
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feedback. Third, unlike solid panels, the text entry task in touch panels needs precise activation on its keys. When key size is small, the key size could be covered by the fingers and result in the wrong keys being activated, thereby lengthening the operation time. Wright et al. (2000) also indicated that one of the problems for small touch screens is key size. Kwon, Lee, and Chung (2009) further set key size as an independent variable and indicated that user performance and preference were improved as the key size increased. As shown in Table 4, the square measurements of key size in HTC legend and iPhone 4G were the first smallest and almost third smallest in all panels. Since the key size of touch panels in this study is relatively small, it may be a possible explanation for the result. Forth, participants reported that the design with one symbol on one key of the touch panel increases the time (including the time for typing mistakes) compared to the design with many symbols on one key of the solid panel; therefore, the overall operation time was extended. Finally, participants were not allowed to use handwriting input function of the touch panel, which might further explain the results. The results also indicated that the frequency of use was significant on operation time (F ¼ 32.954, p , 0.01), demonstrating that the higher the frequency of use, the better the operation performance. The results were in line with those of Forlizzi and Battarbee (2004), who showed that users’ individual experience affects the performance evaluation. Mackenzie, Zhang, and Soukoreff (1999) also indicated that different performances of entry rates occurred among novices, experts and experienced users. Peslak, Ceccucci, and Sendall (2010) further indicated that frequency of use was influenced between young and elder people in text messaging tasks. 4.2. Usability The results indicated that panel type was a significant factor on usability. The results further showed that the usability with the touch and solid panels was significantly better than with the mixed panel. Regardless of whether dealing with vertical or horizontal arrangements of the mixed panel, participants had to seek phonetic symbols of the composite key on the keyboard and then select the word on the touch screen. The shift in hand positioning from the keyboard to the touch screen could result in low usability and long operation time. The results also indicated that no significant difference was found between the touch panel and solid panel. Bangor, Kortum, and Miller (2008) indicated that the mean SUS scores above 52.01 represented an appropriate usability of a product. In this study, the SUS scores of the solid and touch panels were 65.35 and 64.13, respectively. The advantages of the solid panel are its simplicity and consistency. In addition, the selection key and the direction key were in the same area, making it easier for participants to manipulate. For the touch panel, as the simulated keypad appears directly on the screen, except for the one symbol on each key enhancing clarity and ease, participants were not affected by the mapping of the physical keypad. The results of this study concur with the results of Albinsson and Zhai (2003), which pointed out that the touch panel was considered to be participants’ primary user interface with a wider screen and higher flexibility. Therefore, both the touch and solid panels have good usability for sending Chinese text messages. 4.3.
Change of CFF and workload
Panel type, frequency of use and arrangement of phonetic symbols were not significant on change of CFF and workload. A possible reason, also the limitation of this study, was that the operation time is below 10 minutes. Although Iwasaki, Kurimot, and Noro (1989) indicated that the red colour CFF is significantly decreasing after working for 15 minutes with CRT display screens, the screens of mobile displays used in this study were only 2 –4 inches and therefore it is considered that smaller screens could result in more visual fatigue easily. That is why the text entry task was set in the experiment. From the results of this study, it can be inferred that future studies for text entry performance should be conducted with more visual loadings and longer operation time so that the performance of visual fatigue and workload might be significant. Although insignificances were found, we further explained the results from the means. As shown in Table 2, the mean of change of CFF decreased as frequency of use increased and this trend was also found in operation time and usability. This implies that participants with high frequency of use might perform better performance in Chinese text entry tasks. In addition, the mean of change of CFF decreased as the phonetic arrangement moved from horizontal to vertical; this trend was also found in operation time and workload, implying that vertical arrangement might provide a better performance for Chinese text entry tasks. 4.4.
Comparison between operation time and usability
As shown in the results, the operation time of the solid panel is significantly better than that of the touch panel. However, insignificance for usability was found between them. With the growing popularity of the touch panel in the future, users will get used to manipulating the touch panel and therefore the operation time with the touch panel is expected to decrease.
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Although a high operation performance of the touch panel was not obtained, good usability was achieved in this study. Similarly, the performance of the vertical arrangement was significantly better than that of the horizontal arrangement. However, insignificance for usability was found between them. It indicated that participants consider that the horizontal arrangement is also an alternative for usability. This result was in accord with Laarni et al. (2004), which indicated that reading horizontally may be nearly as efficient as reading vertically. Besides, the possible reason for low operation performance could be that participants were not familiar with the horizontal arrangement.
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5.
Conclusion
The main contribution of this study was to explore the effects of panel type, frequency of use and arrangement of phonetic symbols on operation time, usability, change of CFF and workload for Chinese text entry performance. The results indicated that panel type, frequency of use, arrangement of phonetic symbols and the interaction between panel type and frequency of use were significant factors on operation time. The results also demonstrated that the solid panel, high frequency of use and vertical phonetic arrangement provide the best operation performance. In addition, the touch and solid panels showed better usability than the mixed panel. The touch panel showed good usability and the lowest workload in sending Chinese text messages. Since solid panels will be replaced by touch panels in the future and the future design of touch panels should provide people with more advanced and convenient interfaces with high usability, we recommend that people use the touch panel with vertical phonetic arrangement in sending Chinese text messages. Future studies could be conducted to include a text entry task with additional paragraphs of Chinese to investigate the impact on participants’ performance after a prolonged task. In addition, participants reported that they sometimes touched the keys but received no response or even touched the wrong keys when using touch or mixed panels. Therefore, future studies should explore the contact angle and area between the finger and the touch keys as well as the setup of the touch key contact points. References Albinsson, P. A., and S. Zhai. 2003. “High Precision Touch Screen Interaction.” In The CHI 2003 Conference on Human Factors in Computing Systems, edited by Cockton, Gilbert and Korhonen Panu, 105– 112. New York: ACM Press. Bangor, Aaron, Philip T. Kortum, and James T. Miller. 2008. “An Empirical Evaluation of the System Usability Scale.” International Journal of Human-Computer Interaction 24 (6): 574– 594. Brooke. 1996. “SUS: A ‘Quick and Dirty’ Usability Scale.” In Usability Evaluation in Industry, edited by P. W. Jordan, B. Thomas, B. A. Weerdmeester, and I. L. McClelland, 189– 194. London: Taylor & Francis. Chamorro-Koc, Marianella, Vesna Popovic, and Michael Emmison. 2009. “Human Experience and Product Usability: Principles to Assist the Designof User – Product Interactions.” Applied Ergonomics 40: 648– 656. Coleman, E. B., and S. C. Hahn. 1966. “Failure to Improve Readability with a Vertical Typography.” Journal of Applied Psychology 50: 434– 436. Coleman, E. B., and I. Kim. 1961. “Comparison of Several Styles of Typography in English.” Journal of Applied Psychology 45: 262– 267. Dvorak, A. 1943. “There is a Better Typewriter Keyboard.” National Business Education Quarterly 12: 51 – 58. Forlizzi, J., and K. Battarbee. 2004. “Understanding Experience in Interactive Systems.” In The 5th Conference on Designing Interactive Systems, 261– 268. New York: ACM Press. Griffith, R. T. 1949. “The Minimotion Typewriter Keyboard.” Journal of the Franklin Institute 248: 399–436. Hart, S. G., and L. Staveland. 1998. Development of NASA-TLX (Task Load Index): Results of Empirical and Theoretical Research. Amsterdam: Elsevier. Hunnius, S., and R. H. Geuze. 2004. “Developmental Changes in Visual Scanning of Dynamic Faces and Abstract Stimuli in Infants: A Longitudinal Study.” Infancy 6 (2): 231– 255. doi:10.1207/s15327078in0602_5 ISO. 1988. “ISO9241: Ergonomic Requirements for Office Work with Visual Display Terminals (VDTs) – Part 11: Guidance on Usability.” Internation Organization for Standardization. ISO. 2010. “ISO9241-210: Ergonomics of Human System Interaction – Part 210: Human-Centered Design for Interactive Systems.” International Organization for Standardization. Iwasaki, T., S. Kurimot, and K. Noro. 1989. “The Change in Colour Flicker Fusion (CFF) Values and Accommodaction Time during Experimental Repetitive Tasks with CRT Display Screens.” Ergonomics 32 (3): 293– 305. Kwon, Sunghyuk, Donghun Lee, and Min K. Chung. 2009. “Effect of Key Size and Activation Area on the Performance of a Regional Error Correction Method in a Touch-Screen QWERTY Keyboard.” International Journal of Industrial Ergonomics 39: 888– 893. Laarni, J. 2002. “Searching for Optimal Methods of Presenting Dynamic Text on Different Types of Screens.” In The Second Nordic ˚ rhus: ACM Conference on Human-Computer Interaction, edited by Bertelsen, Olav W. Bodker, Susanne and Kuutti Kari, 217– 220. A Press. Laarni, J., J. Simola, I. Kojo, and N. Risto. 2004. “Reading Vertical Text from a Computer Screen.” Behaviour and Information Technology 23 (2): 75 – 82. Lin, M., and A. Sears. 2005. “Chinese Character Entry for Mobile Phones: A Longitudinal Investigation.” Interacting with Computers 17 (2): 121– 146. doi:10.1016/j.intcom.2004.11.003
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