The purpose of the current work is to apply several main principles of the causal explanatory approach for establishing external validity to the experimental arena. By spanning the paradigm of the experimental approach and the school of program evaluation founded by Lee Cronbach and colleagues, the authors address the question of how research…

The authors were asked to find out whether "On Our Way to English" ("OWE"), a supplementary, text-based product to help elementary school students learn to read and speak English was more effective in a California and a Texas school district than the materials the districts already had in place. They conducted an experiment…