Document Type


Date of Degree

Summer 2012

Degree Name

PhD (Doctor of Philosophy)

Degree In

Psychological and Quantitative Foundations

First Advisor

Stephan Dunbar

Second Advisor

Steven B. Robbins


The main purpose of this study was to determine if validity coefficients for ACT scores, both composite scores and subject area test scores, and high school grade point average (HSGPA) decayed or held stable over eight semesters of undergraduate study in science, technology, engineering, and mathematics (STEM) fields at civilian four-year institutions, and whether the decay patterns differed from those found in non-STEM fields at the same institutions. Data from 62,212 students at 26 four-year institutions were analyzed in a hierarchical meta-analysis in which student major category (SMC), gender, and admission selectivity levels were considered potential moderators. Four sets of analyses were run. The first was by the three SMCs: STEM-Quantitative majors, STEM-Biological majors, and non-STEM majors. The second was SMC by gender. The third was SMC by admission selectivity level. The fourth was SMC by gender by admission selectivity level.

The results across all four analyses indicated that ACT score validity coefficients for STEM-Quantitative and STEM-Biological majors decayed less over eight semesters than the validity coefficients for non-STEM majors did. This was true for the uncorrected and corrected validity coefficients. For the HSGPA validity coefficients, this was true for the corrected validity coefficients. Non-STEM majors had very similar validity decay patterns regardless of the level of analysis. However, four of the eight STEM subgroups in the final set of analyses had minimal amounts of decay, and in some instances small amounts of validity growth.


ACT, decay, meta-analysis, stability, STEM, validity


xx, 313 pages


Includes bibliographical references (pages 97-104).


Copyright 2012 Paul Westrick