From the Back Cover
Like many evaluators, we have applied the Campbellian validity typology to outcome evaluations, even though the typology was developed for general research purposes rather than for evaluation specifically. The application to program evaluation has created mixed results. On the one hand, when designing a rigorous outcome evaluation we greatly benefit from the principles and methods highlighted by the typology. The typology enhances our abilities to present or defend the evidence provided from an outcome evaluation. On the other hand, we find that evaluation results often do not meet stakeholders' needs and expectations. The mixed experiences puzzled us, but also motivated us to seek possible solutions as represented in this issue. In general, we take the stance that revising or expanding the Campbellian typology can advance validity in outcome evaluation. Chapter authors present multiple views on how to build on the Campbellian typology's contribution or suggest alternative validity frameworks or models to serve program evaluation better. We hope these perspectives advance theory and practice regarding validity in evaluation, as well as improve the quality and usefulness of outcome evaluations.