A form of outcome evaluation that assesses the net effect of a program by comparing program outcomes with an estimate of what would have happened in the absence of a program. This form of evaluation is employed when external factors are known to influence the program's outcomes, in order to isolate the program's contribution to achievements or its objectives.
US Environmental Protection Agency. (2007). Program Evaluation Glossary. Office of the Administrator/Office of Policy/Office of Strategic Environmental Management/Evaluation Support Division.