ABSTRACT
Plausible alternative explanations are simple hypothetical rival explanations for people's findings. The more they can eliminate them the more legitimate become claims of causality or association. The most plausible alternative explanations are eliminated by using a control or comparison group; some are mitigated by using different but equivalent pre-test and post-test instruments; the threat of some is reduced by carefully training researchers and participants. All experimental and correlational studies must attempt to eliminate as many rival explanations as possible in order to achieve a high degree of internal validity. To eliminate rival explanations is to increase the potential for internal validity. However, potential rival hypotheses are always considered at the outset of, and integrated into the methods of, any good experimental or correlational study. It is especially expected that experimental studies, which make the boldest claims, will introduce all rigor possible to reduce their threat; clearly, it is less possible for correlational studies to do as much.
