Evaluating With Sense

Arguing for more serious theorizing in connection with evaluation, this article shows that although the randomized controlled experiment conceptualized as a "black box" approach has dominated the discussions of impact assessment since the classic statements of Campbell and Stanley (1966), the use of theoretical models in connection with impact assessment can both heighten the power of experimental designs and compensatefor some of the major deficiencies of quasi-experimental designs. The article also emphasizes the importance of theoretical models of implementation processes, arguing that this process often constitutes the major obstacle to the full realization of effective programs.