What if Subjects Can't be Randomly Assigned?

Abstract

Random assignment to treatment is not always possible in evaluative research. The semi-experimental design discussed here has aspects of both full experimental and quasi-experimental designs. Monte Carlo studies are used to explore and exemplify the strengths and weaknesses of the design. The analysis suggested is found to give unbiased estimates of treatment effects and error mean squares but biased estimates of assignment effects. Some further aspects of the design and its use are discussed.