Cohen 1994 - The Earth Is Round (p < .05) Jacob Cohen After...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
The Earth Is Round (p < .05) Jacob Cohen After 4 decades ofsevere criticism, the ritual ofnull hy- pothesis significance testing-mechanical dichotomous decisions around a sacred .05 criterion-stillpersists. This article reviews the problems with this practice, including its near-universal misinterpretation of p as the probability that H o isfalse, the misinterpretation that its complement is the probability ofsuccessful replication, and the mis- taken assumption that if one rejects H o one thereby affirms the theory that led to the test. Exploratory data analysis and the use ofgraphic methods, a steady improvement in and a movement toward standardization in measurement, an emphasis on estimating effect sizes using confidence intervals, and the informed use of available statistical methods is suggested. For generalization, psychologists mustfinally rely, as has been done in all the older sciences, on replication. I make no pretense of the originality of my remarks in this article. One of the few things we, as psychol- ogists, have learned from over a century of scientific study is that at age three score and 10, originality is not to be expected. David Bakan said back in 1966 that his claim that "a great deal of mischief has been associated" with the test of significance "is hardly original," that it is "what 'everybody knows,''' and that "to say it 'out loud' is ...toassumetheroleofthechild whopointed out that the emperor was really outfitted in his under- wear" (p. 423). If it was hardly original in 1966, it can hardly be original now. Yet this naked emperor has been shamelessly running around for a long time. Like many men my age, I mostly grouse. My ha- rangue today is on testing for statistical significance, about which Bill Rozeboom (1960) wrote 33 years ago, "The statistical folkways of a more primitive past continue to dominate the local scene" (p. 417). And today, they continue to continue. And we, as teachers, consultants, authors, and otherwise perpetrators of quantitative methods, are responsible for the rituali- zation of null hypothesis significance testing (NHST; I resisted the temptation to call it statistical hypothesis in- ference testing) to the point of meaninglessness and be- yond. I argue herein that NHST has not only failed to support the advance of psychology as a science but also has seriously impeded it. Consider the following: A colleague approaches me with a statistical problem. He believes that a generally rare disease does not exist at all in a given population, hence H o :P = O. He draws a more or less random sample of30 cases from this population and finds that one ofthe cases has the disease, hence P s = 1/30 = .033. He is not December 1994 • American Psychologist Copyright 1994 by the American Psychologicat Association. Inc. 0003-066X/94/$2.oo VoL 49.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 10/17/2009 for the course MET 387 taught by Professor Dean during the Spring '09 term at Old Dominion.

Page1 / 7

Cohen 1994 - The Earth Is Round (p < .05) Jacob Cohen After...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online