Pre- and Post-planned Evaluation: Which Is Preferable?

This paper compares the advantages and disadvantages o f the "pre-planned" and "postplanned" approaches to evaluating program effectiveness. These evaluative approaches are compared along a number o f dimensions which include: (a) Reliability o f data and the cost o f 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 o f these two evaluative approaches should be employed is presented. One major theme throughout this discussion is that despite the growing interest in and use o f 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 o f their respective strengths and limitations. I N T R O D U C T I O N Over the past decade, the idea of developing systematic, formal evaluat ion plans to assess program effectiveness has gained greater acceptabi l i ty . Clearly, the federal requi rement that all government-sponsored programs allocate 1% of their funds toward evaluat ion activities substantiates this point . In certain cases, there is a requi rement for an evaluation plan prior to ini t iat ion of the program; at o ther times there is simply a requi rement that evaluat ion be done subsequent to program operat ion. Usually, the former, a pre-planned evaluat ion is deemed preferable. This pre-planned approach to evaluat ion is not an unmixed blessing: problems can be created by the pre-planned me thodo logy in addi t ion to those it may solve. The purpose of this paper, therefore, is to ident i fy the potent ia l benefi ts and adverse effects of designing evaluat ion before or after a program is conducted . Fol lowing this we will present a decis ion-making mode l which should help program planners, administrators and evaluators ident i fy those condi t ions under which it is best to employ ei ther the preor post-planned methodo logy . In all, this discussion should help responsible program personnel make bet ter decisions about which evaluat ion me thodo logy to implement and minimize the problems inherent in the use o f the mode l selected.