Stability reliability for elementary-age students on the Woodcock-Johnson psychoeducational battery-Revised (achievement section) and the Kaufman Test of Educational Achievement

Abstract

These two studies examined the stability reliability for the Woodcock-Johnson-Revised (WJ-R;Woodcock & Johnson, 1989) and the Kaufman Test of Educational Achievment (KTEA; Kaufman & Kaufman, 1985) with approximately a 2-week retest interval for elementary-age students. Results indicated that across grade levels, the Broad Reading Cluster for the WJ-R remained stable. Most correlations for the clusters for mathematics and written language as well as the subtests for reading, mathematics, and written language were less than .90. Correlations for all composites and subtests for the KTEA exceeded .90. These data illustrate the need for more specific information in test manuals on test-retest reliability in order to enable examiners to select the most reliable measures.The technical adequacy of achievement tests can be difficult to evaluate because examiner manuals often do not contain sufficient information to enable a thorough evaluation. Information on reliability is particularly problematic. If test results are to be used in making eligibility decisions, evidence for stability of the results should be provided in the examiner's manual. When test results are not stable over relatively short periods of time, conclusions may be based upon error rather than a student's true scores.Test-retest reliability can, and frequently does, vary in terms of the age or grade level of students. Yet, in examiner's manuals for achievement tests, data on test-retest reliability typically are collapsed across several age or grade levels, making it unclear how reliable results are for a particular age or grade level. Thus, to ensure selection of measures that provide results likely to reflect students' true scores rather than error, data on shortterm stability reliability should be available on the basis of age or grade level, or at least for every other age or grade level. Salvia and Ysseldyke (1991) suggested that for achievement measures, a retest interval of 2 weeks is preferable and has been the convention. They also suggested a correlation of .90 as the minimum reliability for tests used in making eligibility decisions.According to Hall (1986) and Hutton, Dubes, andMuir (1992), two of the most popular achievement measures are the Woodcock-Johnson-Revised (W J-R; Woodcock & Johnson, 1989) and the Kaufman Test of Educational Achievement (KTEA; Kaufman & Kaufman, 1985). Although both of these tests have extensive examiner manuals, neither manual provides data on test-retest reliability by age or grade level. Reliability data for the WJ-R are collapsed across ages 5 to 95, and data for the KTEA are collapsed across grades 1 through 6 and 7 through 12.The present studies evaluated the test-retest reliability of the WJ-R and the KTEA in more detail using the conventional 2-week retest interval for students in the elementary grades.