The present authors argued that the covariance analysis is completely valid even if there is a true main effect for pretesting and a second point of the paper involved a recommendation for data analysis if the interaction from ANOVA was significant. (Editor/RK)

Identifying the effects of the New York State Experimental Prekindergarten Program on the development of children requires that a broad array of data be analyzed. In studying the effects of the program, the evaluation unit is interested in determining whether there is an overall effect, and whether children of different ages and different levels…

The four main approaches to measuring treatment effects in schools; raw gain, residual gain, covariance, and true scores; were compared. A simulation study showed true score analysis produced a large number of Type-I errors. When corrected for this error, this method showed the least power of the four. This outcome was clearly the result of the…

Action research often necessitates the use of intact groups for the comparison of educational treatments or programs. This paper considers several analytical methods that might be used for such situations when pretest scores indicate that these intact groups differ significantly initially. The methods considered include gain score analysis of…

When two groups, initially dissimilar, undergo different treatments, can subsequent differences be partitioned in such a way that the difference between the two treatments is unbiased? This is the central problem of this paper, and it is confronted by the examination of two levels of information using a Follow Through Evaluation. The first…

Two methods of reading instruction (homogeneous grouping and graded classes) are compared for 165 students in 8 rural North Dakota schools by raw gain scores, residual gain scores, and the analysis of covariance. (CK)