This study examines the relative effectiveness of two means of analyzing the pre-test/post-test control group experimental design. Samples were randomly drawn from a standardized normal population and assigned to one of the four cells of the design. A set of experimental differences were induced in the post-test experimental cell. Each case was…

The pretest-posttest design referred to as Design 2 by Campbell and Stanley (1963) is commonly used in educational research and evaluation. The tenability of the assumption of a zero population difference commonly used with this design is questioned. A nonzero population estimate based on the mean difference observed in test-retest reliability…