At 11:30 AM 7/12/2008, Bunny, lautloscrew.com wrote:
Hi everybody,somehow i dont get the shapiro wilk test for normality. i just can´t find what the H0 is . i tried : shapiro.test(rnorm(5000)) Shapiro-Wilk normality test data: rnorm(5000) W = 0.9997, p-value = 0.6205 If normality is the H0, the test says it´s probably not normal, doesn ´t it ? 5000 is the biggest n allowed by the test... are there any other test ? ( i know qqnorm already ;) thanks in advance matthias
Yes, H0 is "normality". The P-value, as for other statistical tests, measures the probability that this sample could have arisen from the population under H0.
0.62 is a probability very compatible with H0. The typical rejection criterion would be a P-value < 0.05, which is not the case here.
The limitation to n = 5000 is not serious, as even a few hundred data should take you to the asymptotic region. Use sample() to select the data at random from within your data set to avoid bias in using the test. E.g.,
shapiro.test(sample(mydata, 1000, replace=TRUE)) ================================================================ Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: [EMAIL PROTECTED] Least Cost Formulations, Ltd. URL: http://lcfltd.com/ 824 Timberlake Drive Tel: 757-467-0954 Virginia Beach, VA 23464-3239 Fax: 757-467-2947 "Vere scire est per causas scire" ================================================================ ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
