Date Approved


Degree Type

Open Access Thesis

Degree Name

Master of Science (MS)

Department or School


Committee Member

John Knapp, PhD, Chair

Committee Member

Renee Lajiness-O’Neill, PhD

Committee Member

Dean Lauterbach, PhD


Measurement error at different ability levels in the WISC-IV was studied to empirically test the conditional error variance hypothesis. Graduate students in clinical psychology at a Midwestern university scored fictitious WISC-IV Vocabulary subtests constructed to yield actual scaled scores of 4, 10, and 16. Classical measurement theory assumes error rate will be constant across the three conditions. Modern test theories (Item Response Theory), however, predict that the precision of a measurement instrument will change as a function of the examinee's ability level. Data supported the conditional error variance hypothesis. Scorers made significantly more errors in the low- and high-abilitylevel conditions than they did in the average ability condition. Implications of these findings for intelligence testing are discussed.

Included in

Psychology Commons