A method is proposed for calculating the sample size needed to achieve acceptable statistical power with a given test. The minimally important difference significant (MIDS) criterion for sample size is explained and supported with recommendations for determining sample size. The MIDS criterion is computationally simple and easy to explain. (SLD)

Among the many problems faced by family researchers in conducting experimental research in field settings is that posed by nonequivalent and intact treatment and control groups. Nonequivalence refers to the assignment of individuals to treatments on a nonrandom basis, thus generating treatment groups with different expected values on one or more…

The presence of artifactual bias in analysis of covariance (ANCOVA) and in matching nonequivalent control group (NECG) designs was empirically investigated. The data set was obtained from a study of the effects of a television program on children from three day care centers in Mexico in which the subjects had been randomly selected within centers.…

The regression-discontinuity approach to evaluating educational programs is reviewed, and regression-discontinuity post-program mean differences under various conditions are discussed. The regression-discontinuity design is used to determine whether post-program differences exist between an experimental program and a control group. The difference…

The Penn Manor CRT/Curriculum Articulation Project was designed to study the impact of the implementation of four specific interventions on the achievement of elementary school students in mathematics and language arts. The interventions were as follows: (1) classroom teachers were given individual curriculum skill objectives for their grade…