Abstract
The critical role played by research design has been widely discussed among evaluators. Generally there is a consensus that experimental and certain quasi-experimental designs are preferable for their ability to eliminate or minimize threats to internal validity. Least preferred are the class of nonexperimental designs, particularly the one-group, pretest-posttest design. This design, while convenient, is regarded as incapable of controlling for most standard threats to internal validity. In practical applications, however, this design may be stronger than expected. The context, or situation, in which the design is applied may make one or more standard threats to validity implausible. An example from evaluations at the World Bank Institute is provided to demonstrate the effectiveness of this design within a given situation. It is suggested that evaluators carefully review the plausibility of each threat to design validity within the context to which it is applied as a means of adding to their repertoire of existing evaluation tools.
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