Accompanying this expansion in the size and scope of program evaluation initiatives is the maturation of the field. A clearer understanding of the differing functions played by specific evaluation strategies has been complimented by a clearer sense of those features that are common to all forms of program evaluation. The most important distinction that has been drawn for many years regarding the purpose of program evaluation concerns the use of evaluation processes to determine the worth of a program and the use of evaluation processes to assist in the improvement of this program. The terms used to identify these two functions are formative and summative.

Formative and Summative Program Evaluations

A noted educational researcher, Paul Dressel, differentiated several decades ago between summative evaluation that involves “judgment of the worth or impact of a program” and formative evaluation that Dressel defines as “the process whereby that judgment is made.” The evaluator who is usually identified as the author of this distinction, Michael Scriven, offers the following description of these two terms. According to Scriven, formative evaluation:

. . . is typically conducted during the development or improvement of a program or product (or person, and so on) and it is conducted, often more than once, for the in-house staff of the program with the intent to improve. The reports normally remain in-house; but serious formative evaluation may be done by an internal or external evaluator or (preferably) a combination; of course, many program staff are, in an informal sense, constantly doing formative evaluation.

As described by Scriven, summative evaluation:

. . . is conducted after completion of the program (for ongoing programs, that means after stabilization) and for the benefit of some external audience or decision-maker (for example, funding agency, oversight office, historian, or future possible users), though it may be done by either internal or external evaluators or a mixture. The decisions it serves are most often decisions between these options: export (generalize), increase site support, continue site support, continue with conditions (probationary status), continue with modifications, discontinue. For reasons of credibility, summative evaluation is much more likely to involve external evaluators than is a formative evaluation.