Validity of the MMPI-168 as an Estimate of the Full MMPI

Transcription

1 Western Michigan University ScholarWorks at WMU Master's Theses Graduate College Validity of the MMPI-168 as an Estimate of the Full MMPI Judith Ellen Cohen Western Michigan University Follow this and additional works at: Part of the Psychoanalysis and Psychotherapy Commons Recommended Citation Cohen, Judith Ellen, "Validity of the MMPI-168 as an Estimate of the Full MMPI" (1977). Master's Theses This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact

2 VALIDITY OF THE MMPI-168 AS AN ESTIMATE OF THE FULL MMPI by Judith Ellen Cohen A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the Degree of Master of Arts Western Michigan University Kalamazoo, Michigan August 1977

3 ACKNOWLEDGEMENTS I wish to thank the members of my committee, Dr. Malcolm Robertson, Dr. George Sidney, and especially Dr. John Gallagher, for their assistance and support throughout this project. Additional thanks are due Mr. Brian Mitchell of the Computer Center for his patience and superb programming of my research. Finally, recognition is due to Mrs. Melissa Tatum and Ms. Sandra Bier for their support and help, and most of all to Mr. Mark Barnhouse for his priceless encouragement and assistance through what seemed an endless feat. Judith Ellen Cohen

4 IN F O R M A T IO N TO USERS This material was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1.T h e sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. When an image on the film is obliterated with a large round black mark, it is an indication that the photographer suspected that the copy may have moved during exposure and thus cause a blurred image. You will find a good image of the page in the adjacent frame. 3. When a map, drawing or chart, etc., was part of the material being photographed the photographer followed a definite method in "sectioning" the material. It is customary to begin photoing at the upper left hand corner of a large sheet and to continue photoing from left to right in equal sections w ith a small overlap. If necessary, sectioning is continued again beginning below the first row and continuing on until complete. 4. The majority of users indicate that the textual content is of greatest value, however, a somewhat higher quality reproduction could be made from "photographs" if essential to the understanding of the dissertation. Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. 5. PLEASE NO TE: Some pages may have indistinct print. Filmed as received. University M icrofilm s International 300 North Zeeb Road Ann Arbor, M ichigan USA St. John's Road, Tyler's Green High Wycombe, Bucks, England HP10 8HR

5 MASTERS THESIS 13-10,449 COHEN, Judith Ellen, VALIDITY OF THE MMPI-168 AS AN ESTIMATE OF THE FULL MMPI. Western Michigan University, M.A., 1977 Psychology, clinical Xerox University Microfilms, Ann Arbor, Michigan 48106

6 T A B LE OF CONTENTS PAGE I. INTRODUCTION... 1 II. M E T H O D S u b j e c t s P r o c e d u r e III. R E S U L T S I V. D I S C U S S I O N R E F E R E N C E S iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

7 LIST OF TABLES TABLE PAGE 1. Mean Raw Scores, Standard Deviations, and Correlations of Scale Scores for Standard MMPI and M M P I Intercorrelations among MMPI-550 (Lower Triangle) and MMPI-168A (Upper Triangle) Scales of 766 Outpatient Psychiatric Clients Intercorrelations among MMPI-550 (lower Triangle) and MMPI-168B (Upper Triangle) Scales of 766 Outpatient Psychiatric Clients Correlations of Scaled Scores for MMPI-550 with MMPI-168A; MMPI-550 with MMPI-168B; and MMPI- 168A with M M P I B Means, Standard Deviations, and t Values for All Scales of the MMPI-550, MMPI-168A, and MMPI-168B Comparison of MMPI-550 and MMPI-168A with Respect to Matching of Three Highest Clinical Scales in Any Rank O r d e r Comparison of MMPI-550 and MMPI-168B with Respect to Matching of Three Highest Clinical Scales in Any Rank O r d e r Comparison of MMPI-550 and MMPI-168A with Respect to Ordinal Position of Three Clinical Scales Highest in Rank on Full MMPI (N = 766) Comparison of MMPI-550 and MMPI-168B with Respect to Ordinal Position of Three Clinical Scales Highest in Rank on Full MMPI (N = 766) 25 iv

8 I. INTRODUCTION The Minnesota Multiphasic Personality Inventory (MMPI) is a widely used personality test, primarily for the diagnosis of mental disorders. Due to its widespread application, the length of the complete 550-item MMPI has been the object of considerable concern for the past 23 years. The search for a short version of the test dates back to 1954 when Olson tried simply dropping those items not scored on the standard clinical and validity scales. Kincannon (1968) developed a compact short form of 71 items, the Mini-Mult, which began the recent flow of studies on this form as well as other abbreviated short forms. Graham and Schroeder (1972) added items to the Mini-Mult so that Scales 5 (M f) and Si could be included. The Midi-Mult with 86 items was developed by Dean (1972) in an effort to improve the accuracy of prediction for Scales L, F, and 9 (Ma). Hugo (1971) used multiple linear regression analysis to develop his short form, while Faschingbauer (1972) utilized a cluster analysis of scale items in developing his 166-item short form (the FAM). Spera (1973) developed a 104-item short form containing statements rarely endorsed by normals and useful as screening items. The most recent work was done by Overall and Gomez-Mont (1974) using the first 168 items of the Form R MMPI test booklet, and they entered the data into 1

9 their own multiple linear regression equations to predict the full scale scores. This thesis will be attending to the MMPI-168 short form, specifically. The increasing attention being conferred upon the MMPI short forms is a realistic endeavor due to the clinical situations whereby it is impossible or extremely difficult to administer and interpret the full-length test. Fasching- bauer (1976) explained that many patients are unable to complete all 550 items due to psychiatric difficulties such as restlessness, irritability, or lack of concentration. Others have problems due to poor eyesight, slow reading ability, or some other non-psychiatric impairment. In some cases, patients are permitted to complete the test over several sessions. This option presents difficulty, for example, in assessing the patient's psychotic state upon admission or in an impeded psychomotor state after the prescription of a phenothiazine. This procedure also raises the problem of assessing different behavior by the end of the test-taking sessions than the patient exhibited upon entry. Prompt diagnostic interviewing may be helpful in circumventing this problem; however, this requires valuable professional time. The original intent of the developers of the MMPI was to avoid such an expenditure of initial professional time. Due to the upsurge of computerized automated scoring and interpretation of the MMPI, many mental health facilities utilize this test as a major and mandatory clinical tool for

10 3 assessment upon a patient s initial contact. This raises a problem in the amount of time an incoming patient is willing or able to invest in the initial paperwork for admission. It also raises problems for the budget allotment of a facility in order to incorporate the high costs of key-punching and processing for each MMPI test administered. The difficulties of obtaining a complete MMPI upon admission are clear, and thus few clinicians are willing or able to readminister the test as an objective measure of improvement as a result of hospitalization/psychotherapy. For those who can value the usefulness of the MMPI for suggesting areas for further investigation, correcting for diagnostic biases, and providing a single, brief, easily communicated and stored record of a patient's personality, a short form which could accurately predict the long-form data could be a viable solution to the previously stated problem. In reviewing the recent literature concerning short-form versions of the MMPI, Overall and Gomez-Mont's (1974) MMPI-168 appears to be a likely prospect for the most accurate prediction of the long-form data. Their study consisted of scoring 339 MMPI test records from the medical school and state hospital in Galveston, Texas, using conventional clinical and validity scoring keys. Each record was scored twice, once considering all items scoring on the 3 validity and 10 clinical scales of the first 373 items of Form R, and again

11 considering only the first 168 items. Their decision to use 168 items was based largely on the fact that item #168 appeared as the last item at the bottom of page 7 of Form R test booklet, providing a convenient stopping point in clinical use. Least squares regression methods were used to estimate the (K-scale corrected) conventional MMPI scale scores from the (uncorrected) scores derived from the abbreviated version. Overall and Gomez-Mont found a high degree of similarity in the patterns of intercorrelations. The simple product moment correlations between the two sets of T scores, the full MMPI scores, and the MMPI-16 8 scores ranged from.79 (Ma) through.96 (Hs). These substantial correlations suggested that the abbreviated form was comparable to the conventional MMPI in this regard. On the basis of these findings, they established that most of the information in the conventional clinical scales was well represented in the first 168 items of the MMPI. As a result of the work done by Overall and Gomez-Mont (19 74), Overall, Hunter, and Butcher (1973) thought it reasonable to expect that the factor structure defined by analysis of intercorrelations among the first 168 items should represent rather adequately the factor structure of the complete MMPI. Using 505 psychiatric patients drawn from a state hospital, a hospital inpatient and outpatient unit, the first 168 items of the standard Form R of the MMPI were factor-

12 5 analyzed. This analysis clearly suggested the presence of six independent factors: Somatization, Low Morale, Psychotic Distortion, Depression, Acting Out, and Feminine Preferences. Comparison with other studies of the complete MMPI factor analysis at the item level showed considerable consistency in both number and nature of factors. These factors seem to adequately represent the span of psychiatric disorders: neuroses, anxiety reactions, depression, psychopathy, and major psychotic disturbance by single factors. In order to interpret the clinical significance of factor scores, they computed normal ranges and norms from a sample of 708 college students. The mean scores for the psychiatric patients were sbustantially higher than the normals on all five clinical factors. As expected, the college sample differed least from the psychiatric sample on the Acting Out factor. To examine the validity of the factor scoring based upon the short 168-item test, the proportions of subjects in the normal and psychiatric samples with T scores greater than 70 elevation on one or more factors were determined. In the college sample, 80 out of 708 had an elevated score on one or more factors; and in the psychiatric sample, 439 out of 505 had one or more factor scores elevated. They concluded that the specificity and sensitivity of factor scoring based on the short 168-item form of the MMPI appeared adequate to justify use as a screening instrument. Newmark, Newmark, and Cook (1975) questioned the results

13 of Overall and Gomez-Mont (1974), partly based upon their sample selection of 339 psychiatric inpatients who were primarily alcoholics and from psychiatric outpatients composed largely of neurotic and personality disorder diagnoses. They also thought that analysis of group mean data was insufficient support for the MMPI-16 8, and that analysis of individual profile pairs was critical to demonstrate the utility of a short form. Their 140 subjects (70 male and 70 female) were obtained from the files of psychiatric inpatients at the University of North Carolina School of Medicine, who received the MMPI as standard admission procedure. The MMPI-168 items were extracted, scored, and converted into standard-scale K-corrected raw scores by the same method as Overall and Gomez-Mont (19 74), and then K-corrected T scores were used for profile code interpretation. The raw scores, means, standard deviations, and Pearson product-moment correlations of the comparable validity, clinical, and Mf and Si scales of both the MMPI-168 and the standard MMPI are presented as a function of sex in Table 1. Paired t tests yielded significant differences only on scale EkL, thus the MMPI-168 significantly underestimated the social introversion- extroversion scale. The remaining highly significant scale correlations suggested that the MMPI-16 8 corresponded fairly accurately to the standard MMPI for psychiatric inpatients as a group. Newmark et al. (1975) also had each MMPI profile

14 Scale Table 1 Mean Raw Scores, Standard Deviations, and Correlations of Scale Scores for Standard MMPI and MMPI-168 Males Females MMPI MMPI- 168 MMPI MMPI- 168 M SD M SD r M SD M SD r L * * F * * K * * Hs * * D * * Hy * * Pd * * Mf * * Pa * * Pt * * Sc * * Ma * * Si * * *p <.001 Note. From "The MMPI-168 with Psychiatric Patients" by C. S. Newmark, L. Newmark, and L. Cook, Journal of Clinical Psychology, 1975, 31(1), 63.

15 interpreted independently by two Ph.D. clinical psychologists who were asked to concur on a general diagnosis (psychotic, neurotic, and personality disorder) for each subject. Disagreements in interpretation that could not be resolved in conference were settled by a third psychologist. The two They did not know from which test form the coded profile came, and their ordering differed so that both forms' profile codes were not placed in close proximity. psychologists' diagnoses agreed for 90 percent of the profiles. Additionally, three judges were asked to rate each subject's superimposed plots of both the standard and short-form MMPI profiles on a 4-point scale of similarity (i.e., 1 = no similarity, 2 = slight, 3 = moderate, 4 = marked similarity). In determining the proportion of cases in which the MMPI-168 led to accurate decisions about the validity, high points, and elevations of the corresponding standard MMPI profiles, the MMPI-168 concurred in all but two cases with standard form MMPI decisions denoting validity, and predicted the one or two most elevated scales on the standard form profiles in approximately 72 percent of the cases. A final analysis compared the profile codes of the MMPI forms in terms of consensual diagnosis only. Agreement for general diagnostic categories (psychotic, neurotic, and personality disorders) was 80 percent for males and 86 percent for females, with a combined agreement of 83 percent. Overall, Butcher, and Hunter (1975) compared the

16 9 discriminant validity, for general psychiatric screening, of the MMPI-168 short form with that of the standard Form R, stopping at item 373. They envisioned an important use of the MMPI to be psychiatric screening in seemingly normal populations. The ability of the instrument to discriminate psychiatric patients from normal college students seemed a reasonable basis for comparison of the validity of different scoring procedures. Subjects consisted of 431 mixed clinical problems from a state hospital, referrals of private patients in a university hospital, an inpatient alcohol treatment unit, and an outpatient drug rehabilitation unit. Males outnumbered females 3 to 1. The normal comparison group consisted of 400 MMPI records from a college student sample with approximately the same sex ratio. scored according to four procedures: The tests were (1) standard clinical scoring, (2) clinical scale scoring based on the first 168 items, (3) factor scoring based on the standard Form R, and (4) factor scoring based on the first 16 8 items. Due to the sex composition, Mf scale scores or masculine-feminine factor scores were not considered in these analyses. The use of T > 70 as a cutting point resulted in fewer misclassifica- tions of normals than of psychiatric patients. Also, because there were fewer factor scores than clinical scale scores on which elevations could occur, the proportion classified as abnormal according to factor scoring was lower than for clinical scale scoring. Probably as a matter of chance for

17 1 0 their data, the MMPI-168 scoring yielded fewer errors of classification than did the standard Form R with both factor scoring and clinical scale scoring. The validity of factor scoring and clinical scale scoring appeared comparable when simple T > 70 scale elevation was used as the criterion for abnormality. Next, a simple discriminant function analysis was performed on each of the sets of scores. The discriminant function classification based on the 168-item short form was as accurate as the classification based on the standard form scoring. Having verified high discriminant validity for clinical scale scores estimated from the MMPI- 168 short form through use of regression transformations previously derived by Overall and Gomez-Mont (1974) from a relatively small psychiatric sample, the writers calculated new and more parsimonious regression transformations from the larger combined psychiatric and college student sample of this study. These were derived without additional scales being included in the equations. The conclusion of this study indicated that the MMPI-168 short form has the potential for providing as valid general psychiatric screening as does the standard form. The clinical scale scores derived from the MMPI-16 8 have potential equivalence to those derived from the long form for general psychiatric screening. The final study to be reviewed is Newmark, Falk, and Finch (1976), in which they investigated the comparative

18 interpretive accuracy of three abbreviated MMPI's with the standard MMPI using a sample of 165 psychiatric inpatients. Subjects were tested approximately hours after admission, and a counterbalanced design was used to offset evidence of decreased psychopathology on repeated MMPI administrations. Subjects were randomly assigned to one of three groups and received both the standard form of the MMPI and one of the three short forms; the Faschingbauer abbreviated MMPI (FAM; Faschingbauer, 1972), the Hugo short form (Hugo, 1971), or the MMPI-168 (Overall & Gomez-Mont, 1974). The tests were given in a counterbalanced order, with a 2-8 hour test-test interval. Newmark interpreted each MMPI profile with only relevant demographic data available for each subject. Interpretations of both forms for each subject of approximately words were then presented to a psychiatric team in charge of primary care for that patient. Approximately one week later, the team was asked to rate the accuracy of each interpretation on a 5-point scale (i.e., 1 = total inaccuracy, 2 = 25-percent accuracy, 3 = 50-percent accuracy, 4 = 75-percent accuracy, and 5 = 100-percent accuracy). Interpretation ratings on the standard MMPI were significantly higher than those obtained on the FAM (t = 2.30, p.05) and also than the Hugo (t = 7.88, p.001). In contrast, no significant differences occurred for the interpretive ratings of the standard MMPI and the MMPI-168. For the standard MMPI and MMPI-168, 88 percent and 86 percent

19 12 of the interpretations, respectively, were rated as either 4 or 5. There were obvious limitations of this study: the principle of sampling applied only to the subjects and not in the selection of interpreters; no rules were given by the interpreter regarding his interpretation procedure; no interjudge reliability was available nor was the test-retest reliability of each judge presented; and there was no substantiation that the 5-point accuracy scale was a true-equal interval scale. However, the investigators concluded that there was evidence to suggest that the interpretations of the MMPI-168 were comparable in accuracy to those of the standard MMPI form. The purpose of this study was to cross-validate Overall and Gomez-Mont's (19 74) findings using their multiple regression equations to convert MMPI-16 8 raw scores into predicted long-form raw scores, and Newmark et al.'s (1975) correlations of the MMPI-168 with the long form, the proportion of cases in which the MMPI-168 accurately predicted high-point elevations of the long form, and the significant difference on scale S_i. This study was also used to validate Overall et al.'s (1975) simple regression equations as a replacement for the multiple regression equations. made to cross-validate.factor analysis. There was no attempt Two of the four studies used standard scoring on the Form R which is being replaced by the Group Form. Most of the subjects used in the previous studies have been from inpatient psychiatric

20 1 3 facilities and state hospitals. This investigator attempted to cross-validate the previous findings in a large, diversified sample of outpatient psychiatric subjects to determine the degree of generalization to this population as well. Through this study of the literature, the investigator believes that the MMPI-168 short form has the greatest potential for accurately predicting the standard long-form MMPI clinical scores and profiles. There appears to be no need to develop a new format of the test because no items of the first 168 have been changed, added, or deleted. Since the items appear in context and customary sequence, data that are already on clinical files can be used to validate the procedure. Oftentimes, patients are unaware as to how far they must go in the test booklet when they start the test, and even if they do know, stating a terminal item number should not effect their performance. Should a patient be unable or unwilling to finish the full form of the test and has reached at least #168, the MMPI-168 may be used to score the incomplete form. The MMPI-168 short form can also be used for scoring either the Group Form or Form R of the full MMPI because the first 300 items are the same for both. Another benefit of the MMPI-16 8 for both staff and patients is that it requires approximately one-third of the time necessary to complete the long form. Unlike other short forms, no scales have been omitted from the MMPI The only apparent difficulty with the MMPI-168 is that it tends

21 1 4 to underestimate the S^L scale for both sexes. However, this scale is one of the least relevant clinical scales on the MMPI, and has only minimal significance in diagnostic interpretation. The only liability with the short form as developed by Overall and Gomez-Mont (1974) is their regression equations. The long multiple regression equations have numbers taken to three decimals which make conversion computations extremely lengthy. Therefore, this investigator will also be testing the comparative effectiveness of Overall et al.'s (1975) simple linear regression equations to correct for this liability. Another advantage of the shorter equations is the simplified calculation of a conversion table for the MMPI-168. The general hypotheses which will be tested in this study are as follows: (1) the MMPI-168 short form accurately predicts the clinical and validity scales of the MMPI-550 long form; (2) the MMPI-168 predicts MMPI-550 long-form profiles for interpretation by means of accurately labeling the two or three high elevation points of the Welsh Code; and (3) Overall et al.'s (1975) simple linear regression equations (after K-correction) are equivalent to Overall and Gomez-Mont's (1974) multiple linear regression equations in predicting long-form raw scores from MMPI-168 data.

22 II. METHOD Subjects The raw data for this study were derived from 766 keypunched MMPI-550 long-form tests taken from the files of the William Upjohn DeLano Memorial Clinic, an outpatient mental health unit in Borgess Hospital, Kalamazoo, Michigan. The subjects were composed of 287 males ranging in age from 16 through 68 (mean = 30 years), and 479 females ranging in age from 15 through 65 (mean = 30 years). These subjects were given the MMPI individually upon intake to the clinic using the standard written instructions of the Form R test booklet. These 766 subjects comprised 53 percent of the open cases for DeLano Clinic for the fiscal year covering July 1, 1974, through June 30, Therefore, the demographic data of these subjects have been generalized for that fiscal year from the annual DeLano Clinic statistical report produced by the Michigan Department of Mental Health, report number H , as follows: 1. Ethnic group a. Caucasian b. Black c. Other 97% 2 1% 2. Education level a. None-eighth grade 10% b.. Some high school 29 c. High school graduate 34 15

23 16 d. Some advanced school 16% e. College graduate 10 f. Miscellaneous 1% 3. Marital status a. Never married 20% b. Married 52 c. Separated 10 d. Divorced 12 e. Widowed 3 f. Unknown 2% Average income level a. $0 - $6,000 53% b. $6,001 - $10, c. $10,401 or over 9 d. Social Security/Public Assistance 19 e. Unknown 1% Procedure This study used computer programming of the standard scoring key for the full scale test, K-correction, table for the Hs, Pd, Pt, S, and Ma scales, and the Adult Norms T-score table (Hathaway & McKinley, 1967) for the three validity and 10 clinical scales. cards were scored in three ways: Each subject's key-punched (1) raw scores for the MMPI-550 were K-corrected and transformed into T scores; (2) raw scores from the first 168 items were converted into predicted long-form K-corrected raw scores using Overall and Gomez-Mont's (1974) multiple regression equations, and then transformed into T scores \MMPI-16 8A); and (3) raw scores from the first 16 8 items of the long form were converted into predicted long-form raw scores using Overall et

24 al.'s (1975) simple regression equations, were K-corrected, and were then transformed into T scores (MMPI-168B). The program also reported the three highest clinical scale elevations, in descending order, of T scores of each profile for the MMPI-550, the MMPI-168A, and the MMPI-168B. In cases where two or more scales had equal T-score values, the program reported all those scales as being included in the given level of the high-point elevations. The investigator used the top three scales as high-point elevations for the results. If there were two or more equal T scores for the third level, they were used interchangeably in the comparison tests. Therefore, when there was a tie between two or more scales for either the second or third level of the high points, all the equal scales were used as possible matches. For instance, if the second and third high point in one profile of the MMPI-550 matched two equal scales at the third level of the MMPI-16 8A, then the investigator recorded this as a one-point match in the total matches in any order and as a two-point match in the ordinal rank position.

25 III. RESULTS Intercorrelations among scales within the profiles of the MMPI-550, MMPI-168A, and the MMPI-16 8B were computed to examine similarities of patterns. The intercorrelations among the T scores of all three sets of profiles are presented in Tables 2 and 3. Subjectively, these intercorrelations appear to demonstrate an acceptable degree of similarity. The Pearson product-moment correlations of the clinical and validity scaled scores for the MMPI-550 with the MMPI- 168A, the MMPI-550 with the MMPI-168B, and the MMPI-168A with the MMPI-168B are presented in Table 4. The correlations for the MMPI-550 with the MMPI-168A ranged from.79 (scale Si) through.94 (scale D). For the MMPI-550 with the MMPI- 168B, correlations ranged from.76 (S_±) through.94 (scale D ). The correlations for the MMPI-16 8A with the MMPI-168B ranged from.94 (scales Mf, Pa, Si) through 1.0 (scales F, D, Hy). In order for the Pearson product-moment correlation (r) to be statistically significant at the.01 level for a sample of 700 pairs, r must be equal to or greater than.097. All the obtained correlations are highly significant. Table 5 presents the means, standard deviations, and r values for all scales of the MMPI-550, MMPI-168A, and MMPI- 168B. Paired t tests resulted in the largest differences 18

26 19 being significant at the.001 level on scales Sc and Si between the MMPI-550 and the MMPI-168A. Other significant differences are noted in Table 5. Tables 6 and 7 present the number and percentages of matches in any rank order of the three high-point clinical scale elevations for the MMPI-550 with the MMPI-168A and the MMPI-550 with the MMPI-168B. In comparing the 766 profiles of the MMPI-550 with those of the MMPI-168A, the results show that 649 of the profiles (84 percent) had matched on the two or three highest clinical scale elevations irrespective of ordinal position. Comparison of the 766 profiles of the MMPI-550 with those of the MMPI-168B resulted in 675 profiles (88 percent) matching on the two or three highest clinical scale elevations irrespective of ordinal position. Tables 8 and 9 present the percentage of correspondence between the MMPI-550 and the MMPI-168A as well as the MMPI- 550 and the MMPI-168B with respect to ordinal position of the three clinical scales highest in rank.

27 Table 2 Intercorrelations among MMPI-550 (Lower Triangle) and MMPI-168A (Upper Triangle) Scales of 766 Outpatient Psychiatric Clients L F K L F K Hs D Hy Pd M f Pa Pt Sc Ma Si to o

28 Table 3 Intercorrelations among MMPI-550 (Lower Triangle) and MMPI-168B (Upper Triangle) Scales of 766 Outpatient Psychiatric Clients L F K L F K Hs D Hy Pd Mf Pa Pt Sc Ma Si

29 MMPI-550 with MMPI-168A MMPI-550 with MMPI-168B MMPI-168A with MMPI-168B Table 4 Correlations of Scaled Scores for MMPI-550 with MMPI-168A; MMPI-550 with MMPI-168B; and MMPI-168A with MMPI-168B L F K Hs D Hy Pd Mf Pa Pt Sc Ma Si to to

30 Table 5 Means, Standard Deviations, and t Values for All Scales of the MMPI-550, MMPI-168A, and MMPI-168Ba MMPI- 550 MMPI-16 8A MMPI-168B M SD M SD t M SD t L F * ** K Hs D Hy Pd Mf Pa Pt ** Sc ** Ma ** ** Si ** * Means and standard deviations are derived from the T scores. *Significant difference with MMPI-500 at.01 level (2-tailed Fisher's t test). **Significant difference with MMPI-550 at.001 level (2-tailed Fisher's t test). to Co

31 24 Table 6 Comparison of MMPI-550 and MMPI-168A with Respect to Matching of Three Highest Clinical Scales in Any Rank Order Number of Matches Total Number of profiles Percent Table 7 Comparison of MMPI-550 and MMPI-168B with Respect to Matching of Three Highest Clinical Scales in Any Rank Order Number of Matches Total Number of profiles Percent

32 25 Table 8 Comparison of MMPI-550 and MMPI-168A with Respect to Ordinal Position of Three Clinical Scales Highest in Rank on Full MMPI (N = 766) Rank on MMPI-168A Rank on MMPI-550a Lower aall in percentages. Table 9 Comparison of MMPI-550 and MMPI-168B with Respect to Ordinal Position of Three Clinical Scales Highest in Rank on Full MMPI (N = 766) Rank on MMPI-168B Rank on MMPI-550a Lower a All in percentages.

33 IV. DISCUSSION The substantial correlations between the long form and both short forms of the MMPI indicated that the MMPI-168 short form accurately predicted the clinical and validity scales of the MMPI-550 long form. Comparison of the correlations in the present study between the MMPI-550 and the MMPI- 168A with those from the study done by Overall and Gomez- Mont (1974) demonstrated a high degree of similarity. Comparison of the correlations in the present study between the MMPI-550 and the MMPI-168A with both the male and female correlations shown by Newmark et al. (1975) also demonstrated a high degree of similarity, except for notable differences on scales Mf and Ma. The present study's MMPI-168A exceeded the female Mf scale correlation of the Newmark study by as much as.10 and was lower for Newmark's male Ma scale correlation by as much as.16. These differences may have occurred by chance fluctuation in the larger sample of the present study. Another factor which might account for these discrepancies is the difference in population characteristics of the present study from the earlier one, such as the use of outpatient subjects rather than inpatient or the nearly 2 to 1 ratio of females to males as opposed to equal numbers of each. The high correlations found between the MMPI-168A and 26

34 27 the MMPI-168B indicated that Overall et al.'s (1975) simple linear regression equations (after K-correction) were nearly equivalent to Overall and Gomez-Mont's (19 74) multiple linear regression equations in predicting long-form raw scores from MMPI-168 data. Therefore, the present investigator recommends the use of the simple linear regression equations developed by Overall et al. (19 75) for the conversion computations of the MMPI-168 short form. This set of equations simplifies the calculations and makes possible the development of a convenient table for the conversion of MMPI-168 raw scores into predicted MMPI long-form raw scores. Paired t tests on the mean differences between the MMPI-550 and both MMPI-168 short-form versions indicated significant differences on scales Pt, Sc, Ma, and Si of the MMPI-168A and scales F and Ma of the MMPI-168B. The largest differences occurred on scales Sc and Sfi for the MMPI-168A. These results support previous findings by Newmark et al. (1975) that the MMPI-168 multiple regression equations underestimate scale SM of the standard MMPI. No significant differences were found for either the Si_ or Sc scales of the MMPI-168B, thereby supporting the use of the simple regression equations, keeping in mind the slight overestimation of scales F and M a. Another result of this study concerning scale c presented an additional finding. Of the 766 cases, 317 of the MMPI-550 profiles showed scale S to be greater than or equal

35 28 to a T score of 80. For every one of these cases, the MMPI- 168A consistently underestimated scale Sc: 19 percent by 1-14 points, 59 percent by points, and 29 percent by 26 points or over. However, for these same cases, the differences on the MMPI-168B appeared to proportion themselves into an almost normal distribution with 11 percent of the cases reported equal to that of the MMPI-550. Yet, the MMPI-168A and MMPI-168B both obtained an r =.85 with respect to the MMPI-550 scale Sc. In order to ascertain the reason behind these equal correlations, the investigator reviewed the remaining 449 profiles of T scores less than 80 to see if the MMPI-168A more often overestimated the long-form scale Sc. For the cases where the MMPI-550 scale Sc: was a T score below 80, the MMPI-16 8A overestimated 13 percent by 1-14 points, and underestimated 68 percent by 1-14 points and 13 percent by points. The MMPI-168B overestimated the full-form scale Sc 45 percent by 1-14 points and 11 percent by points, and underestimated these cases 33 percent by 1-14 points and 3 percent by points. Again, the MMPI-168A more often underestimated scale Sc of the long form even when the T scores were below 80, and the MMPI-168B was close to normally distributed. Considering these results in conjunction with the significant mean difference on scale Sc for the MMPI-168A and MMPI-550, this study supports the use of analysis of differences between means in addition to correlational analysis in evaluating the predictability of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission

36 29 this short form. Further research in this area may ascertain the possibility of this phenomenon occurring in other scales for the multiple regression equations' predictability of long-form raw scores. The results of this study also indicated that MMPI-168 predicted MMPI-550 profiles for interpretation by means of accurately predicting the two or three high elevation points of the Welsh Code in 84 percent and 88 percent of the 766 cases. The MMPI-168B exceeded the MMPI-168A in correctly predicting the two or three high points of the MMPI long form in any ordinal position. The present study also considered the MMPI-168's ability to predict ordinal position of the MMPI long-form clinical scale high-point elevations. These data are important because most profile interpretations are constructed on the basis of the two, and sometimes three, highest clinical scale T-score elevations. The most significant fact taken from Tables 8 and 9 is that the MMPI-168A and MMPI-168B accurately predicted the first highest clinical scale elevation of the long form in 4 8 percent and 51 percent of the total cases, respectively. The first highest elevation of the MMPI-168A and MMPI-168A matched the first or second high-point elevations of the long form in 73 percent and 74 percent of the total cases, respectively. Finally, the second highest elevation of the MMPI-168A and MMPI-168B matched the first or second high-point elevations of the long form in 44

37 30 percent and 52 percent of the total cases, respectively. Newmark et al. (1975) established that in 72 percent of their combined male and female cases, the MMPI-168 accurately predicted the highest clinical scale. The present investigator questions the generalizability of Newmark's results because he dismissed 52 of the 140 possible profiles for interpretation as invalid if any validity scales were equal to or greater than 70 T. Consequently, Newmark decreased the number of profiles which were compared and deleted profiles which other clinicians may deem significant, thereby limiting the generalization of his findings to a very specific set of profiles. On the other hand, this investigator included all profiles regardless of the magnitude of the validity scales. Therefore, in comparing the results of the present study to those of Newmark et al. (1975), the present study's MMPI-168 appeared to match the highest clinical scale of the long form less often. The present study's lower percentages may be due to the inclusion of all profiles regardless of the validity scales. The results of this study support the hypothesis that the MMPI-168 short form effectively predicts the two highest clinical scale elevations of the MMPI long form either in exact or reversed order, and therefore that the MMPI-168 is likely to produce profile interpretations comparable to those of the long form. As with the individual profile matches in any order, the group data analysis of matched ordinal

38 31 positioning also demonstrates the superiority of the simple regression equations over the multiple regression equations in matching the first and second highest T-score elevations for clinical scales. In conclusion, for a psychiatric outpatient population the results of the study indicate that the MMPI-168 short form is capable of accurately predicting the clinical and validity scales of the MMPI-550 long form. This short form can also predict the two or three highest clinical scale elevations of the long version with a sizable degree of accuracy, and therefore can be used interchangeably with long-form profiles for interpretation. The advantages previously stated for the MMPI-168, as well as the results of this study, favor the use of the MMPI-16 8 short form as an alternative to the standardized long form. These results also support the use of the simple linear regression equations developed by Overall et al. (1975) for conversion of the 168-item test into predicted long-form raw scores because of the complex calculations required for the multiple regression equations as well as their underestimation of both the Si and Sc scales. The reader should also note that when using the simple regression equations, scales F and Ma have been shown to slightly overestimate the means for those same scales of the long form of the MMPI.

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40 Overall, J. E., Hunter, S., & Butcher, J. N. Factor structure of the MMPI-168 in a psychiatric population. Journal of Consulting and Clinical Psychology, 1973, 41(2), Spera, J. A. A 104-item short form of the MMPI: The Maxi- Mult (Independent research project). Unpublished manuscript, Western Michigan University,