normality test
Le 28.04.2005 13:16, Pieter Provoost a ??crit :
Hi, I have a small set of data on which I have tried some normality tests. When I make a histogram of the data the distribution doesn't seem to be normal at all (rather lognormal), but still no matter what test I use (Shapiro, Anderson-Darling,...) it returns a very small p value (which as far as I know means that the distribution is normal). Am I doing something wrong here? Thanks Pieter
Hello, You seem to know not far enougth. Null hypothesis in shapiro.test is **normality**, if your p-value is very small, then the data is **not** normal. Look carefully at ?shapiro.test and try again. Furthermore, normality tests are not very powerful. Consider using a ?qqnorm and ?qqline Romain
~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~ ~~~~~~ Romain FRANCOIS - http://addictedtor.free.fr ~~~~~~ ~~~~ Etudiant ISUP - CS3 - Industrie et Services ~~~~ ~~ http://www.isup.cicrp.jussieu.fr/ ~~ ~~~~ Stagiaire INRIA Futurs - Equipe SELECT ~~~~ ~~~~~~ http://www.inria.fr/recherche/equipes/select.fr.html ~~~~~~ ~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~