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…

To determine if the ethnocentric perceptions of students would be influenced by participation in a 3-week social studies unit on "The Contributions of Minority Ethnic Groups to American Civilization," a study was made utilizing 114 students in five 12th grade social studies classes (three experimental and two control). The investigation attempted…