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.
Scriven borrows from Bob Stake in offering a less formal but perhaps more enlightening distinction between formative and summative: “When the cook tastes the soup, that’s formative; when the guests taste the soup, that’s summative.” From an appreciative perspective, formative evaluation can be said to be an exercise in fully understanding the complex dynamics and causal factors influencing the operation of a program. By contrast, a summative evaluation allows one to identify and build on the specific successes and strong features of a specific program unit. Both formative and summative evaluations can be appreciative. The comprehensive appreciation of any program unit involves both formative and summative evaluation processes.
Ed Kelly, an experienced program evaluator from Syracuse University, further differentiated judgments concerning the extent to which the intentions of the program were satisfied and judgments concerning whether or not the program was any good. Concern for judgment necessarily involves issues of values, criteria, goals, customers and audience; concern for evaluative process necessarily involves issues of method, instrumentation and resources. Both approaches to evaluation require a clear definition of clientship, a precise sense of the role of evaluation and an explicit understanding of the way the judgment or process will be used by the program staff and others.
