Nudging aside Meehl's paradox
| Autor: | Les Leventhal |
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| Rok vydání: | 1994 |
| Předmět: | |
| Zdroj: | Canadian Psychology / Psychologie canadienne. 35:283-298 |
| ISSN: | 1878-7304 0708-5591 |
| DOI: | 10.1037/0708-5591.35.3.283 |
| Popis: | Meehl (1967) attacked significance tests used to appraise directional theoretical predictions. With perfect statistical power, the probability approaches .5 of significance in the predicted direction -- even for meritless theories. Feeble theory corroboration results. I argue that directional predictions, not significance tests, produce the feeble corroboration. I review previous solutions to Meehl, rejecting all except the multiple corroboration solution by Lykken (1968) and Kukla (1990). I defend this solution against Meehl's criticisms (Meehl, 1990b) and extend it: The complexity of a typical research design enables a theory to make multiple directional predictions, each of which can be adequately tested with a significance test. Reasonable theory corroboration results when all or most predictions succeed and I discuss techniques to assess this.Paul Meehl, in a classic paper (Meehl, 1967), assailed the use of significance tests to appraise theories in "soft" psychology (e.g., clinical, counseling, developmental, personality, and social psychology). Meehl repeated his attack in 1978 (Meehl, 1978), and a reply to Meehl by Serlin and Lapsley (1985) generated a great deal of work (Dar, 1987; Campbell, 1990; Chow 1990; Dar, 1990; Fiske, 1990; Humphreys, 1990; Kimble, 1990; Kitcher, 1990; Kukla, 1990; Maxwell & Howard, 1990; McMullin, 1990; Meehl, 1990a, 1990b, 1990c, 1990d; Rorer, 1990; Serlin & Lapsley, 1990). Increasingly philosophical and decreasingly accessible to the psychologist, this work departed greatly from Meehl's attack without resolving it. Indeed, many of the more philosophical papers did not even mention it. The purpose of this paper is to bring the focus back to Meehl's attack, to provide a critical review of previous solutions, and to offer my own response.Meehl's ParadoxMeehl (1967) described a paradox which illustrates the harm that evaluating theories with significance tests can do to soft psychology. His summary:Because physical theories typically predict numerical values, an improvement in experimental precision reduces the tolerance range and hence increases corroborability. In most psychological research, improved power of a statistical design leads to a prior probability approaching 1/2 of finding a significant difference in the theoretically predicted direction. Hence the corroboration yielded by "success" is very weak, and becomes weaker with increased precision. (p. 103)The paradox compared psychology and physics on the consequences of increased experimental precision to theory - testing research. (Increased experimental precision results from improved experimental design, instrumentation, or numerical mass of data.) The paradox claimed that, in physics, increases in experimental precision in theory - testing research result in larger hurdles for theories to negotiate and therefore more credibility for theories when theoretical predictions are corroborated; however, in psychology, which appraises theories by evaluating theoretical predictions with significance tests, increases in precision result in smaller hurdles for theories to negotiate and therefore less credibility for theories when predictions are corroborated. Meehl said that this paradox stems from two facts. First, while physics theories typically make point predictions, that is, predict exact or nearly exact numerical values (often bounded by a range of probable error), psychology theories typically make directional predictions, that is, predict that the relationship between an independent and dependent variable will be either positive or negative. Second, psychologists test their theories with significance tests, constructing a directional alternative hypothesis to express the theory's prediction and claiming theory corroboration when data reject the null in favour of the alternative hypothesis.(f.1) Meehl (1967) argued that these two facts produce the paradox, and Meehl's argument is summarized below by 8 points. … |
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