Updating the debate on one- versus two-tailed tests with the directional two-tailed test

Journal/Book: Psychol Rep. 1999; 84: P O Box 9229, Missoula, MT 59807, USA. Psychological Reports. 707-718.

Abstract: For half a century, methodologists have debated wen to use one-and two-tailed tests. But they conducted the debate with scarcely a mention of the little known directional two-tailed test-the only hypothesis test that, properly used, provides for a decision in either direction. In contrast, the traditional two-tailed test assesses nondirectional statistical hypotheses and does not provide for a directional decision. A directional two-tailed test with unequal rejection regions can have virtually the same power as a one-tailed test and, unlike one-tailed tests, it provides for deciding in the unpredicted direction. However, a problem unresolved for one-tailed tests remains for the directional two-tailed test, namely, whether one should create unequal rejection regions just because one has grounds to predict an outcome's direction. Nevertheless, the directional two-tailed test will satisfy research needs much more frequently than will traditional tests and should be adopted as the primary, general-purpose hypothesis test.

Note: Article Leventhal L, Univ Manitoba, Dept Psychol, Winnipeg, MB R3T 2N2, CANADA

Keyword(s): LISTENING TESTS; SIZE

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