This is one of a series of eight short monographs intended to aid practicing educators in planning and conducting accountability programs in schools. This booklet discusses how to develop an experimental design appropriate to the objectives of a particular research or evaluation effort. Short sections focus in turn on the characteristics of a good experimental design, factors to consider in evaluating an experimental design, examples of weak experimental designs, examples of strong experimental designs, and extensions of good experimental designs. Written exercises are included at the end of the booklet to enable readers to assess their understanding of the material presented. (Author/JG)