CORRESPONDENCE ACROSS THREE ETHNIC GROUPS OF CONSTRUCTS MEASURED BY THE IOWA TESTS OF BASIC SKILLS

BRUCE THOMPSON, HERBERT L. ALSTON, AND MICHAEL W. SAY

Houston Independent School District

A random sample of all sixth-grade students enrolled in a large urban school district completed the Iowa Tests of Basic Skills. Tests were administered by either a counselor or a teacher to groups composed of no more than six stu- dents. The corres ondence of test vectors measured by the test was analyzed. Results su gest tfat the ITBS does not measure exactly the same constructs across stufient ethnic groups.

Achievement tests have come under increasing criticism in the last decade. One of these criticisms is based on the consistent finding that individuals coming from different ethnic groups systematically perform differently on achievement tests; thus, it is asserted that some achievement tests actually measure different things in different pupil groups. The use of an achievement test in a general school population, therefore, raises the question of whether the instrument measures the same constructs across the different population ethnic groups.

Kaiser, Hunka, and Bianchini (1969) proposed a procedure for estimating the correspondence of a set of constructs across different groups. The extent to which the same constructs are measured for two groups by an instrument is indicated by the cosines of the test vectors for the constructs for each group. These cosines can be interpreted as correlation coefficients. Using this procedure, the study reported here addressed the question of whether three basic skills subtests of the Iowa Tests of Basic Skills (ITBS) measure the same constructs for Anglo Americans, Negro Americans, and Mexican American ethnic groups.

METHOD Subjects

The subjects were a 6% random sample of all sixth-graders enrolled in a large southwestern metropolitan school district. Of the 867 students identified through the sampling procedure, 310 students were from the Anglo American ethnic group; 368 students were from the Negro American ethnic group; and 189 students were from the Mexican American ethnic group. Approximately half of the students were males and half were females. These students completed the Iowa Tests of Basic Skills in small groups of no more than six students under the supervision of a teacher or counselor. Procedure

All items were scored right equal one, or wrong equal zero. Then a stratified random sample of 100 items from three basic skills subtests (Reading Comprehension, Mathematics Concepts, and Mathematics Problem Solving) was drawn. Finally, these items were factor analyzed separately for the three ethnic groups, using Rao’s (1955) canonical analysis procedure. The extracted factors were rotated to the varimax criterion. Canonical factor analysis was used because the procedure as- sumes that a given correlation matrix is based upon a sample of cases and asks what

Requests for reprints should be sent to Bruce Thompson, Program Planning, Research and Evaluation Dept., Houston Independent School District, 3830 Richmond Ave., Houston, TX 77027.

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348 Psychology in the Schools, July, 1978, Vol. 16, No. 3.

the most likely population parameters would be. Thirty-six statistically significant factors were extracted from the correlation matrix associated with the Anglo American students. Forty statistically significant factors were extracted from the correlation matrix associated with the Negro American students. Thirty-nine statistically significant factors were extracted from the correlation matrix associated with the Mexican American students. The type of factor analysis used does not affect the relative position of the test vectors (c.f. Tryon & Bailey, 1970), but it is of interest to note that approximately the same number of factors were identified for each ethnic group.

The correspondence of the ITBS items was measured by the procedure proposed by Kaiser, et al, (1969) utilizing a program by Veldman (1967). This procedure involves the rotation of the structure with the smaller number of factors to a position of best fit with the test vectors of the larger of the two factor structures being com- pared. The cosines of the test vectors indicate the degree of correspondence of the constructs (Kaiser, et al., 1969). The mean of these cosines indicates the degree to which the instrument as a whole measures the same set of constructs across groups.

RESULTS AND DISCUSSION The correspondence of the ITBS items across the three ethnic groups was only

moderate. The mean correspondence of the Anglo American and Negro American groups was .63 (SD = .098). The mean correspondence of the Negro American and Mexican American groups was .59 (SD = ,099). The mean correspondence of the Anglo American and Mexican American groups was -62 (SD = .089).

A substantial portion of variance associated with the test vectors was shared across ethnic groups; however, a somewhat larger portion of variance associated with the test vectors was not shared across ethnic groups. Kaiser, et al., (1969) suggest that .85 be used as a rough criterion for determining whether a test measures the same constructs across groups. Thus these results do not support a conclusion that the three subtests of the Iowa Tests of Basic Skills measure exactly the same constructs across ethnic groups. There are several possible sources of this variation.

First, the students may not have tried to do well on the test. However, since special efforts were made to motivate students to apply themselves during the testing session, it may be assumed that the niajority of students appIied themselves on the test. Second, low correspondence of test vectors might be caused by bias within the test itself. However, if the limited correspondence of the test vectors was due to test bias, one would expect substantial variance in the correlations among the vectors. That is, culturally biased vectors should have smaller correlation coefficients than the vectors in general. But in this study, as the standard deviations of the correlations suggest, the coefficients cluster very closely together.

By process of elimination, the results make plausible the possibility that the limited correspondence of the test vectors may be associated with characteristics of the students themselves. For example, some students may systematically per- form poorly as a consequence of deprivation which tends to lessen achievement motivation and restrict exposure to certain learning opportunities.

In summary, educators should be cautious in assuming that the Form 5 Level 12, Iowa Tests of Basic Skills measures the same constructs across ethnic groups.

Correspondence Across Ethnic Groups 349

However, educators can not a,ssume, based on this evidence alone, that these dis- crepancies arise purely as a function of test bias.

REFERENCES KAISER, H. F. HUNKA, S., & BIANCHINI J. Relating factors between studies baaed upon different

individuak. In H. J. Eysenck & S. $. G. Eysenck (Eds.), Personality structure and measurement. San Diego, CA: Knapp, 1969, pp. 333-343.

Estimation and tests of significance in factor analysis. Psychometrika, 1955, 20, 92-111. Cluster analysis. New York: McGraw-Hill, 1970.

Fortran programming for the behavioral sciences. New York: Holt, Rinehart, &

RAO, C. R. TRYON, R. C., & BAILEY, D. E. VELDMAN, D. J.

Winston, 1967.

COMPARISON OF THE WISC-R AND PPVT FOR A GROUP OF MENTALLY RETARDED STUDENTS

HUBERT “BOONEY” VANCE

James Madison University

KAREN K. PRICHARD AND FRED H. WALLBROWN

Wichita State Universily

This study compared the WISC-R and PPVT scorm for a grou of 65 students classified as mentally retarded, ranging in age from 7.5 to 14.5. $earson product momenta (r) and correlated t values were em loyed in the analysis of data. The evidence from the present study indicatefthat for this sample of mildly retarded children and youth, the PPVT I& score is si ificantly higher than the Full Scale I& from the WISC-R. The current fintifngs indicate that the same general pattern exists for the WISC-R and PPVT as for the WISC and PPVT scores.

A number of studies (Kimbrell, 1960; Pasewark, Fitzgerald, & Gloeckler, 1971; and Thorne, Kaspar, , & Shulman, 1965) have reported correlations between the Wechsler Intelligence Scale for Children (WISC, Wechsler, 1949) and the Peabody Picture Vocabulary Test (PPVT, Dunn, 1959) for mentally retarded children. These studies generally indicate substantial, significant correlations (rs) between the PPVT and the WISC Verbal Scale I& and Full Scale I&, with nonsignificant correlations between the PPVT and WISC Performance Scale I&. Even though 72% of the items (Sattler, 1974, p. 511) in the WISC are contained in the Wechsler Intelligence Test for Children-Revised (WISC-R, Wechsler, 1947), there is little research available dealing with how, or if, the item changes have affected either correlations originally obtained with the WISC and PPVT or the tendency for PPVT IQs to be somewhat higher than those from the WISC.

Consequently, the present study was designed to determine whether significant differences exist between WISC-R I& scores and the PPVT I& scores for mentally retarded children and youth. The magnitudes of any significant differences were also of concern, since this information should prove useful to psychologists using the two tests. The correlations (rs) among these four I& scores were also included, since the data were already available to compute them. Such correlations are potentially useful to clinicians working with mentally retarded persons.

Requests for re rind should be sent to Hubert Vance, Child Study Center, JamesMadison University, Harrisoniurg, VA 22801.