Journal of Personality Assessment
ISSN: 0022-3891 (Print) 1532-7752 (Online) Journal homepage: http://www.tandfonline.com/loi/hjpa20
Confidence Intervals for the MMPI--2 Patrick H. Munley To cite this article: Patrick H. Munley (1991) Confidence Intervals for the MMPI--2, Journal of Personality Assessment, 57:1, 52-60, DOI: 10.1207/s15327752jpa5701_8 To link to this article: http://dx.doi.org/10.1207/s15327752jpa5701_8
Published online: 10 Jun 2010.
Submit your article to this journal
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Citing articles: 1 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=hjpa20 Download by: [Nanyang Technological University]
Date: 06 November 2015, At: 15:58
JBLXNAL OF PERSONALITY ASSESSMENT, 1991, 5?(1), 52-60 Copyright c 1901, Lawrence Eribaum .4asocrates I n c
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
Confidence Intervals for the
The cct~fidenceintervals for the Minnesota Makiphasic Personaiiry Inventory (Mh4Bi-2) iiinicci scales were investigated. Rased or, the c!ir.ical scale :eiiaSllities nubiished :n thc MMPI-2 r;..anual, es:imateci :rue scores, standard errors of mensuremenc f3r estimated true scores, and 05% confidence intervals centered around estizatecl true scores were caiculzted at $ p i n t h4.llc';PI-2 T-score intervais. The reiationships between obtained T-scores, estimated true T-scores: scaie reiiabilities, and co~fidence~nterwissre discussed. The ?ossibie role of error measurrnent in deficing scaie high poin: and ccldc rypei: is noted.
The Mh4Pi-i manual (Butcher, Dahlsrrom, Grabax, Teilegen, & Kaemmer, .i-359)provides a n ursdated and restandardized version of the MMK. The MhlPi-2 ail! ilkel\. continue in the tradition of the M h l Z as one of rhe most t-,= 2,~aentIy used perscnality fests in rhe Uriited Srates (lu'sin, Larsen: & h.lacarazzs, i9.54).A n appreciaticm of the rel~abiiirvo f t h e scaies of the tesr an2 :he potential infiuence of error measurement in scale scores and profile configz~rariocis important for those interprering ihe tes:. The new MktPI-2 manua! $u:cher et a:., 1989) reports data on the rest-retest reliability of the scales and the raw score standard errors of measurement. ~ m p h a s i sis piaced cn the inrportzice of users adopting t i e practice of sketching in the range of *I standard error o!measurement sround the original raw score or! the basic scales. As note$ in the new manuai, sensitivity to the limfts of the r.-Iiabiiiry of any t inrerpreting profile patterns parcicuiar score o n the inventory is i m p o r t a ~ in and in evaluating changes obtained across adminisrracicns. Butcher et 21. (1989) reported reliability coeificients for bask clinical scales without K correction i j r a community sanpie of men and women, wi:h 2 median rest-rerest interval of I week, For men, the clinical scale reliability n
-ir
-
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
or; rive adrrr:cistracioris, about one h u r r h to one third of :he schjecti had rb,e same 2-painr code, and about one fourth o i the subjec:~had the sarne 3-poinr code. Grahsm et ai. ii986l f ~ u : ~tesr-reresr d ag=reeXents fcr higE;.-;?~inr. Icw. . ? o m , E I 2-poiri: ~ mde types in a sample ofmaie a n t fexaie psvch:arric patients Code rypes tenjed :o be more of 4i.32%, 4-3.9596.and 27.65%, respectii~el~. stable when scales in :he coiie type had more extreme eievmons ini:iai!y and %-henscores on the scales in :he code y p e s were rxrkeiiiy iiseren: iron other scdes in the Frofile. Giver. :he emphazis in the MhPI ixerpretative Literaxre c?r,h4MPI code types te.g., s:ngie t.,igh-?oirL:; L-pcmt, an2 3-point c:& :\yes;, information concerr;iag confidence intervals 3:' h4S4PI and L!h4?I-2 siores m a v . . . be important i s uncierstandi:~~ and inteqxeting cb:ained stores and ortameci scsre code rvpes. , Siherstein i!i)82f discussed two methods o i setting confidence intervals tar tes: scnres: rhe conventior,al method and the technicail.; correct method. The " " c e n v r ~ t i o n amethod i is based or: &rained :esr scot-e~ i;X! srd the stanszra error ofmeasuremcct (SErn). T i e techn:caiiv correct method :I. based on t!-~eestinareii trde score ;'?I aand the standard errcr o i measurement for esrixated true sccsre,, S~rn(?:~ The formnla for the comwxiona! method is as ioilows: q
.
?
-
where X is a person's obtained tes: score, i, is the standard ;score ,,.due in a fiarmai discribstior, associared with a specific conficience in:er,,-ai ( i.32 h r 6E30. 1.96lor 45Bi, and SEmiXj is the standard error of meascrernent for obtair:e3 scores. This traditional x e t b o d c-rf c a i d a t i n g a:d centering the x ~ f i d e n c e interval about obtaineci: scores. is considered to be incorrec: !N;ir.naiIv. 137F; Stanley, 1% I because :he method does not take intc account regress:m :c>u.ar; :he mean due to errors of measxrernen:. Siiverstein IZ9E;'i': ncxed :ha: although :here has been agreement :hat the ionfiderlce intermi shcald be centered sr!a
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
persor:'s ?- to account for regression to the mean associated with errors of meassrernent, rhere has beer! some conhsion ir, the iiterature about which standard error to utilize with f. The recommended standard error {or the confidence interval centered on the Tie rhe S E n for ;i'(Glutting, McDerrnott, & S:anley, 1987;Silverstein, 1989; Stanley, 1971). The formula for es:irr,ating 4:from the obtsined score is:
he~e r = rehebthty of :he rest: X = the obtained score, and M = the mean. The formula for the confidence interval about :he f is given by. ~l
where Z 1s :he standard :score vzhe assocrated with a designated confidence h standard error of measurement for estmateci true scores mterval. ~ ~ m 1stthe $\,en by:
The relationships berween ?s and X an2 between SEE for Ts and X is apparent from the formdas. A person's i i ' d equai X when X = M or the test has perfect reiiability (i.2). In orher cases, j'wil be closer to .;he M than X.The SEm oC Ts is smaller than :he SEm fer Xs unless the test has perfecr reliabiiit:;. Xunnaily (1978':noted that in most applied work, X is most appropriate!:; Coninterpreted; however, confidence intervals should be centered around iidence intervals cenrered about are asymnetricai :o X and have the practical advantage of continually reminding test users that the scores on any test tend to be biased outward on both sides of M. Giver: the role and interpretive significance of extrene scores in the MMPI irirerpretative literature ie.g., singk high-point codes, 2-poir;t codesj, exploration of confidence intervais centered about Ts ooi the MMPZ-2 appears important. The purpose of this study was to investigate ccnfidence intervals for. MMPi-2 T-scores without I( correction centered on Ts.
T.
METHOD
k ithis studg, the relisbilides presented in Tables D-i and D-2 of the Mh?PI-2
-
manua! (Butcher et al., 2989) were used for calcularing the without Kcorrection !-score SEms for each basic clinical scale for men and wornel-:. In each case, the clinical scale 7-score standard deviation of IO was multiplied times the square root of I minus the reliabilitv coefficient of the sc.zie. The ii' for each T-score
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
RESULTS
DISCUSSION
men an2 wemen, severai clbseri-atlox are noted xhich n x y be of inceresr :o . . c!!:lrc:ans. Firs:, the reiar~onshjgs be:ween :sf Xs,and scaic reliabili:v a x e v i d e ~ tfrom an inspection oi :ne rabies. ;he higher the scaie rcl:abiiiry, the . . -cioser the I :s ro X and the smaller the codidence iccervd is around the r . i he Icwrr the scaie re1iabiI:r-y cueffkicnr, :he cioser the ?' :s tc? X? versus X 7;nirk a larger confidence interw2 centered abour ?. This highiights. the iacr tha: certair: ," ?v$?\lF! c h i d scales, particsIzri-y those with iower reliabihy coetiicienrs, msv he rnore likely to show rnore regressio:: to :he .V associxed wi:h error rneasxren e n r on retesting. For example, Scaie 6 fzr both men and aTomer;is ore iike!~ to s h c a more regressior, to the M associated with err-: measurerrmx cln . . reresang than the o t l x clinical scaIes because Scale 6 has the iowest cl:nica! scaie rel~abiiitp. A seconci po:n:, illustrated iR the rabies, is that the amsun: ofregressic~ti? the ?. expecred I or, r e r e s ~ n gassociated wkh error neas;aw-xnr is greater sccres at the extremes of the scaies thar, for scores cioser t ~9. ) : he extem c i ~ o s s i b k%as i:- ext-erne scak scores is reflected in the fact rhar some exreme scale scores are nor even mciudes in the 95% coriiidence i ~ r e r v a cenrere6 l abost -. ? . !s. For e n a z g k , obtained c h c a l l-scores across manv :I: the c h i d scales above T-score v z l ~ e si?i !X are nor in rhe 95% c:snfidence ~nte:\.al c e ~ t z r e d abost TI whi& is lower than X.This reflec:. the amount iii regresslon r s :':i iikeiy ra bt. associated wirh errzrs ~f measurement on retesting based e n the scale rciiability coef5c:ents. As Xs approach the scale M , the difference between Xs +. anti i s :S s m a h , with Xs fa'iiing closer to the center of the 95'0 cenfidence i n t e r i d centered about T. The exact relationsh:p between Ns and cc.nfi&nie 7 .
1
-
7
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
TASLE I Nmety-five Percent Confidence Intervals Male MMPJ-2 Clin~caIScaies
intervals centered about depends on scale reiia'sility and the degree of deviation Q! X from M.Another point, apparent in the tables, is that the size of
ISSN: 0022-3891 (Print) 1532-7752 (Online) Journal homepage: http://www.tandfonline.com/loi/hjpa20
Confidence Intervals for the MMPI--2 Patrick H. Munley To cite this article: Patrick H. Munley (1991) Confidence Intervals for the MMPI--2, Journal of Personality Assessment, 57:1, 52-60, DOI: 10.1207/s15327752jpa5701_8 To link to this article: http://dx.doi.org/10.1207/s15327752jpa5701_8
Published online: 10 Jun 2010.
Submit your article to this journal
Article views: 9
View related articles
Citing articles: 1 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=hjpa20 Download by: [Nanyang Technological University]
Date: 06 November 2015, At: 15:58
JBLXNAL OF PERSONALITY ASSESSMENT, 1991, 5?(1), 52-60 Copyright c 1901, Lawrence Eribaum .4asocrates I n c
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
Confidence Intervals for the
The cct~fidenceintervals for the Minnesota Makiphasic Personaiiry Inventory (Mh4Bi-2) iiinicci scales were investigated. Rased or, the c!ir.ical scale :eiiaSllities nubiished :n thc MMPI-2 r;..anual, es:imateci :rue scores, standard errors of mensuremenc f3r estimated true scores, and 05% confidence intervals centered around estizatecl true scores were caiculzted at $ p i n t h4.llc';PI-2 T-score intervais. The reiationships between obtained T-scores, estimated true T-scores: scaie reiiabilities, and co~fidence~nterwissre discussed. The ?ossibie role of error measurrnent in deficing scaie high poin: and ccldc rypei: is noted.
The Mh4Pi-i manual (Butcher, Dahlsrrom, Grabax, Teilegen, & Kaemmer, .i-359)provides a n ursdated and restandardized version of the MMK. The MhlPi-2 ail! ilkel\. continue in the tradition of the M h l Z as one of rhe most t-,= 2,~aentIy used perscnality fests in rhe Uriited Srates (lu'sin, Larsen: & h.lacarazzs, i9.54).A n appreciaticm of the rel~abiiirvo f t h e scaies of the tesr an2 :he potential infiuence of error measurement in scale scores and profile configz~rariocis important for those interprering ihe tes:. The new MktPI-2 manua! $u:cher et a:., 1989) reports data on the rest-retest reliability of the scales and the raw score standard errors of measurement. ~ m p h a s i sis piaced cn the inrportzice of users adopting t i e practice of sketching in the range of *I standard error o!measurement sround the original raw score or! the basic scales. As note$ in the new manuai, sensitivity to the limfts of the r.-Iiabiiiry of any t inrerpreting profile patterns parcicuiar score o n the inventory is i m p o r t a ~ in and in evaluating changes obtained across adminisrracicns. Butcher et 21. (1989) reported reliability coeificients for bask clinical scales without K correction i j r a community sanpie of men and women, wi:h 2 median rest-rerest interval of I week, For men, the clinical scale reliability n
-ir
-
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
or; rive adrrr:cistracioris, about one h u r r h to one third of :he schjecti had rb,e same 2-painr code, and about one fourth o i the subjec:~had the sarne 3-poinr code. Grahsm et ai. ii986l f ~ u : ~tesr-reresr d ag=reeXents fcr higE;.-;?~inr. Icw. . ? o m , E I 2-poiri: ~ mde types in a sample ofmaie a n t fexaie psvch:arric patients Code rypes tenjed :o be more of 4i.32%, 4-3.9596.and 27.65%, respectii~el~. stable when scales in :he coiie type had more extreme eievmons ini:iai!y and %-henscores on the scales in :he code y p e s were rxrkeiiiy iiseren: iron other scdes in the Frofile. Giver. :he emphazis in the MhPI ixerpretative Literaxre c?r,h4MPI code types te.g., s:ngie t.,igh-?oirL:; L-pcmt, an2 3-point c:& :\yes;, information concerr;iag confidence intervals 3:' h4S4PI and L!h4?I-2 siores m a v . . . be important i s uncierstandi:~~ and inteqxeting cb:ained stores and ortameci scsre code rvpes. , Siherstein i!i)82f discussed two methods o i setting confidence intervals tar tes: scnres: rhe conventior,al method and the technicail.; correct method. The " " c e n v r ~ t i o n amethod i is based or: &rained :esr scot-e~ i;X! srd the stanszra error ofmeasuremcct (SErn). T i e techn:caiiv correct method :I. based on t!-~eestinareii trde score ;'?I aand the standard errcr o i measurement for esrixated true sccsre,, S~rn(?:~ The formnla for the comwxiona! method is as ioilows: q
.
?
-
where X is a person's obtained tes: score, i, is the standard ;score ,,.due in a fiarmai discribstior, associared with a specific conficience in:er,,-ai ( i.32 h r 6E30. 1.96lor 45Bi, and SEmiXj is the standard error of meascrernent for obtair:e3 scores. This traditional x e t b o d c-rf c a i d a t i n g a:d centering the x ~ f i d e n c e interval about obtaineci: scores. is considered to be incorrec: !N;ir.naiIv. 137F; Stanley, 1% I because :he method does not take intc account regress:m :c>u.ar; :he mean due to errors of measxrernen:. Siiverstein IZ9E;'i': ncxed :ha: although :here has been agreement :hat the ionfiderlce intermi shcald be centered sr!a
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
persor:'s ?- to account for regression to the mean associated with errors of meassrernent, rhere has beer! some conhsion ir, the iiterature about which standard error to utilize with f. The recommended standard error {or the confidence interval centered on the Tie rhe S E n for ;i'(Glutting, McDerrnott, & S:anley, 1987;Silverstein, 1989; Stanley, 1971). The formula for es:irr,ating 4:from the obtsined score is:
he~e r = rehebthty of :he rest: X = the obtained score, and M = the mean. The formula for the confidence interval about :he f is given by. ~l
where Z 1s :he standard :score vzhe assocrated with a designated confidence h standard error of measurement for estmateci true scores mterval. ~ ~ m 1stthe $\,en by:
The relationships berween ?s and X an2 between SEE for Ts and X is apparent from the formdas. A person's i i ' d equai X when X = M or the test has perfect reiiability (i.2). In orher cases, j'wil be closer to .;he M than X.The SEm oC Ts is smaller than :he SEm fer Xs unless the test has perfecr reliabiiit:;. Xunnaily (1978':noted that in most applied work, X is most appropriate!:; Coninterpreted; however, confidence intervals should be centered around iidence intervals cenrered about are asymnetricai :o X and have the practical advantage of continually reminding test users that the scores on any test tend to be biased outward on both sides of M. Giver: the role and interpretive significance of extrene scores in the MMPI irirerpretative literature ie.g., singk high-point codes, 2-poir;t codesj, exploration of confidence intervais centered about Ts ooi the MMPZ-2 appears important. The purpose of this study was to investigate ccnfidence intervals for. MMPi-2 T-scores without I( correction centered on Ts.
T.
METHOD
k ithis studg, the relisbilides presented in Tables D-i and D-2 of the Mh?PI-2
-
manua! (Butcher et al., 2989) were used for calcularing the without Kcorrection !-score SEms for each basic clinical scale for men and wornel-:. In each case, the clinical scale 7-score standard deviation of IO was multiplied times the square root of I minus the reliabilitv coefficient of the sc.zie. The ii' for each T-score
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
RESULTS
DISCUSSION
men an2 wemen, severai clbseri-atlox are noted xhich n x y be of inceresr :o . . c!!:lrc:ans. Firs:, the reiar~onshjgs be:ween :sf Xs,and scaic reliabili:v a x e v i d e ~ tfrom an inspection oi :ne rabies. ;he higher the scaie rcl:abiiiry, the . . -cioser the I :s ro X and the smaller the codidence iccervd is around the r . i he Icwrr the scaie re1iabiI:r-y cueffkicnr, :he cioser the ?' :s tc? X? versus X 7;nirk a larger confidence interw2 centered abour ?. This highiights. the iacr tha: certair: ," ?v$?\lF! c h i d scales, particsIzri-y those with iower reliabihy coetiicienrs, msv he rnore likely to show rnore regressio:: to :he .V associxed wi:h error rneasxren e n r on retesting. For example, Scaie 6 fzr both men and aTomer;is ore iike!~ to s h c a more regressior, to the M associated with err-: measurerrmx cln . . reresang than the o t l x clinical scaIes because Scale 6 has the iowest cl:nica! scaie rel~abiiitp. A seconci po:n:, illustrated iR the rabies, is that the amsun: ofregressic~ti? the ?. expecred I or, r e r e s ~ n gassociated wkh error neas;aw-xnr is greater sccres at the extremes of the scaies thar, for scores cioser t ~9. ) : he extem c i ~ o s s i b k%as i:- ext-erne scak scores is reflected in the fact rhar some exreme scale scores are nor even mciudes in the 95% coriiidence i ~ r e r v a cenrere6 l abost -. ? . !s. For e n a z g k , obtained c h c a l l-scores across manv :I: the c h i d scales above T-score v z l ~ e si?i !X are nor in rhe 95% c:snfidence ~nte:\.al c e ~ t z r e d abost TI whi& is lower than X.This reflec:. the amount iii regresslon r s :':i iikeiy ra bt. associated wirh errzrs ~f measurement on retesting based e n the scale rciiability coef5c:ents. As Xs approach the scale M , the difference between Xs +. anti i s :S s m a h , with Xs fa'iiing closer to the center of the 95'0 cenfidence i n t e r i d centered about T. The exact relationsh:p between Ns and cc.nfi&nie 7 .
1
-
7
Downloaded by [Nanyang Technological University] at 15:58 06 November 2015
TASLE I Nmety-five Percent Confidence Intervals Male MMPJ-2 Clin~caIScaies
intervals centered about depends on scale reiia'sility and the degree of deviation Q! X from M.Another point, apparent in the tables, is that the size of
