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Article #290Re: Testing for Normality
From: Jerry Dallal
Date: Sun, 06 Sep 1992 16:09
Date: Sun, 06 Sep 1992 16:09
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In article <thompson.715720959@hermes.socsci.umn.edu>, thompson@atlas.socsci.umn.edu (T. Scott Thompson) writes: > bateman@nsslsun.nssl.uoknor.edu (Monte Bateman) writes: > >>I would like to test data for normality. The books I have >>access to talk about graphing frequencies on "probability paper". > > Look up the Kolmogorov-Smirnov (sp?) statistic in a more advanced > statistics text than the ones you have now. A clarification: Using the K-S statistic to test for normality, calculated after plugging in the sample mean and variance in place of the population parameters, is known as Lilliefors' [Strunk and White be damned!] test. A Shapiro-Wilk test or a D'Agostino test would probably serve you better. Lilliefors' test tends to be more sensitive to departures from normality in the center of the distribution. (One look at the test statistic will reveal why.) THe other tests tend to be more sensitive to departures from normality in the tails, which is where non-normality is most often a problem. This various tests have been compared most recently in, of all places, the Stata Technical Bulletin. I dislike mentioning articles in a computer program's documentation/house organ because they are typically neither peer reviewed nor widely circulated, but it's there, so what can I say? (I have heard rumors that Royston is preparing his contributions for formal publication, but they are only second hand rumors.)
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Path: arc1-ca.pugleaf.net!sparky!uunet!gatech!darwin.sura.net!wupost!micro-heart-of-gold.mit.edu!bu.edu!news.tufts.edu!sage.hnrc.tufts.edu!jerry From: jerry@ginger.hnrc.tufts.edu (Jerry Dallal) Newsgroups: sci.math.stat Subject: Re: Testing for Normality Message-ID: <1992Sep6.110952.349@ginger.hnrc.tufts.edu> Date: 6 Sep 92 16:09:52 GMT References: <1992Sep5.064647.15570@constellation.ecn.uoknor.edu> <thompson.715720959@hermes.socsci.umn.edu> Organization: USDA HNRC at Tufts University Lines: 27