Assessment Measure Review Rowan University Correction of Learning Disabilities Denise A. Johnson
IDENTIFYING INFORMATION Name of Tool: Wechsler Individual Achievement Test – (WIAT –II) Second Edition Publisher: PsychCorp Harcourt Assessment, Inc. 19500 Bulverde Road San Antonio, TX 78259, USA Publication Date: 2005 Qualifications Necessary Professionals who are involved in psychological or educational testing and who have training in the use of individually administered assessment instruments are qualified to administer and interpret the WIAT-II. In all cases, examiner should have training in the fundamental principles of assessment procedures, understand psychometric statistics, scores and interpret tests, and maintain security. Only individuals who have received professional training in educational or psychological assessment should interpret the WIAT-II results.
It offers standard scores, percentile ranks, stanines, and other scores, based either on the student’s age (four-month intervals for ages 4 through 13, one-year intervals for ages 14 through 16, and one interval for ages 17 through 19) or the student’s grade (fall, winter, and spring norms for grades Pre-K through 8, full-year norms for grades 9 through 12, and separate college norms), compared to a random, stratified, nationwide sample of 3600 students. About 9% of the students were identified as having educational disabilities, but not serious neurological disorders. All students spoke English.
A sample of 1,069 students was given both the WIAT-II and a Wechsler Intelligence Scale so that examinees’ WIAT-II scores can be compared to achievement scores predicted from their intelligence scale scores on the basis of actual test scores from the sample. Achievement scores predicted from intelligence tests fall closer to the mean (standard score 100, percentile rank 50) than the intelligence scores from which they are predicted.
Skills Assessed: Subtests assessed are Word Reading, Reading comprehension, Pseudoword Decoding, Numerical operations, Math Reasoning, Spelling, Written Expression, including Alphabet Writing, Word Fluency, Word Count, Listening Comprehension, Oral Expression. Culturally Unbiased The proportions of Whites, African American, Hispanics, Asians, and other racial/ethnic groups for each age-based and grade-based standardization. The break down was as follows: White65%, African American 15%, Hispanics 13%, Asian 5%, other 1%. RELIABILITY DATA (CHAPTER 6): The reliability of the WIAT-II was determined by using the data on internal consistency, test-retest stability, and interscorer reliability demonstrated a high level of precision. Correlations for composite scores ranged from .87 to .99. Several statistics were used, including internal consistency and precision, (split half reliability) interitem comparison, standard error of measurement and confidence interval, test-retest stability and interscorer agreement. The WIAT-II possesses moderately high to high interterm reliability with average reliability coefficients ranging from .80 to .98. The overall total composite reliability is .98. Validity Correlation between the WIAT-II scores and scores on other achievement tests provide evidence that the WIAT-II is a valid measure of achievement for constructs such as math reasoning (labeled ―Mathematical Applications‖ in some achievement test.)
The sizeable differences between the scores of the examinees in the standardization sample and those of examinees in the various clinical groups, such as examinees in gifted programs or examinees diagnosed with mental retardation, also verify the construct validity of WIAT-II interpretations. Two prominent trends were noted in the correlation studies between the WIAT—II and other individually administered achievement tests. First, correlation coefficients among the scores on the reading-related, mathematics, and spelling subtests of the WIAT-II and those of the corresponding subtests of the WIAT. Standard Error of Measure To construct the confidence interval: Age Based Standard Errors of Measurement of the Subtest and Composites. Please refer to Table 6.2 from the WIAT-II Examiner’s Manual. This Table displays the Age Based Standard Error of Measurement of Subtests and Composites.
Standard Scores AVAILABLE SCORES: Age and grade-based Standard Score information; age and grade based Composite Score information; Percentile Ranks, Stanines and NCEs; Age and Grade Equivalents. By age (M = 100, SD = 15 with a range of 40 to 160. By grade (M = 100, SD = 15 with a range of 40 to 160, with separate Fall, Winter, and Spring tables for Grades PreK-8 and yearly tables after Grade 8. Format All subtests except Written Expression have a reverse rule, a discontinue rule, or both, that necessitate scoring he response during test administration. The scoring procedure for Word Reading, Numerical Operations, Spelling, Pseudoword Decoding, Math Reasoning and Listening Comprehension are objective. The responses are scored dichotomously (0 points for an incorrect response, 1 point for a correct response) by using the correct responses that appear on the examiner’s pages of the stimulus booklet or on the record form.
Reference: The Wechsler Individual Achievement Test, Second Edition, Examiners Manual Update 2005