Unavoidable sample size issues beset psychological research that involves scarce populations or costly laboratory procedures. When incorporating longitudinal designs these samples are further reduced by traditional modeling techniques, which perform listwise deletion for any instance of missing data. Moreover, these techniques are limited in their…

This report examines the differences in impact estimates and standard errors that arise when these are derived using state achievement tests only (as pre-tests and post-tests), study-administered tests only, or some combination of state- and study-administered tests. State tests may yield different evaluation results relative to a test that is…

Assessment data are presented from a representative sample of California public school students in grades 4 through 12 in 115 school districts as of December, 1986. The sample represents 5% of the state's enrollment in grades 4 through 12. Students were tested in reading comprehension, writing, and computation. In grade 12, 9,250 students took one…