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Social research frequently encounters the task of evaluating change produced in nonrandomly selected groups by events which are beyond the researcher's control. The social scientist must verify that there has in fact been a change, and that the indicated event is its cause. Illustrations are manifold: a state terminates capital punishment, and proponents of this type of punishment predict an increase in the murder rate; a school is integrated, and supporters of the reform expect to find an increase in the positive self-evaluation of Negro pupils; a natural disaster occurs in a community, and altruistic behavior is expected to increase. Because in these situations the investigator has no control over the assignment of individuals or groups to “experimental” and “control” situations, the logic of the classical experiment must be reexamined in a search for optimal interpretative procedures.
Campbell et al. (Thu,) studied this question.
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