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Raffeld, Paul; Reynolds, William M. – 1977
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…
Descriptors: Control Groups, Correlation, Experimental Groups, Hypothesis Testing
Cunningham, Grover – 1968
A study was conducted to determine if the observed changes in Head Start children were related to the practice effects inherent in a test-retest situation. The "control" group consisted of 64 children who had been eligible for a Head Start program. They roughly matched a group of Head Start (HS) children in IQ scores, age, and…
Descriptors: Cognitive Tests, Control Groups, Disadvantaged, Experimental Groups