Wikis > Evaluation Tools > Before-and-After Comparisons
Primary Source: Patton, C. V, and Sawicki, D. S. (1993) Basic Methods of Policy Analysis, Second Edition. Prentice Hall: Englwood Cliffs, NJ.


Perhaps the most widely used evaluation method, the before-and-after approach, involves comparing conditions (of peoples or locales) before a policy or program is implemented and after it has had a chance to make an impact. Although steps might be taken to identify program objectives and relevant evaluation criteria and to collect data prior to program implementation (rather than to reconstruct the data or rely on data collected for other purposes), this method requires that we assume that any differences between before-and-after data are a result of the policy or program.

This approach can be modified somewhat to compare actual postprogram data with no-action alternative as it was projected before implementing the program. This variation still fails to identify unanticipated consequences of no action and requires us to assume that the trend extrapolation reflects what would have indeed occurred.