Pre- and post-planned evaluation: Which is preferable?

Abstract

This paper compares the advantages and disadvantages of the "pre-planned" and "post-planned" approaches to evaluating program effectiveness. These evaluative approaches are compared along a number of dimensions which include: (a) Reliability of data and the cost of collecting it; (b) Internal validity; (c) External validity; (d) Evaluation obtrusiveness and threat; and (e) Program goal displacement and program direction. A model designed to help program managers decide when and under what conditions either of these two evaluative approaches should be employed is presented. One major theme throughout this discussion is that despite the growing interest in and use of pre-planned evaluation, the post-planned method has many advantages which often go unnoticed. This paper will help program administrators, planners and evaluators in selecting and implementing these two methods in light of their respective strengths and limitations.