Is two-tailed testing for directional research hypotheses tests legitimate?

This paper demonstrates that there is currently a widespread misuse of two-tailed testing for directional research hypotheses tests. One probable reason for this overuse of two-tailed testing is the seemingly valid beliefs that two-tailed testing is more conservative and safer than one-tailed testing. However, the authors examine the legitimacy of this notion and find it to be flawed. A second and more fundamental cause of the current problem is the pervasive oversight in making a clear distinction between the research hypothesis and the statistical hypothesis. Based upon the explicated, sound relationship between the research and statistical hypotheses, the authors propose a new scheme of hypothesis classification to facilitate and clarify the proper use of statistical hypothesis testing in empirical research. (C) 2012 Elsevier Inc. All rights reserved.