Re: [R] Looking for transformation to overcome heterogeneity of variances

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Thu 03 Aug 2006 - 23:45:10 EST

"Paul Smith" <phhs80@gmail.com> writes:

> Dear All
>
> My data consists in 96 groups, each one with 10 observations. Levene's
> test suggests that the variances are not equal, and therefore I have
> tried to apply the classical transformations to have homocedasticity
> in order to be able to use ANOVA. Unfortunately, no transformation
> that I have used transforms my data into data with homocedasticity.
> The histogram of variances is at
>
> http://phhs80.googlepages.com/hist1.png
>
> Is someone able to suggest to me a transformation to overcome the
> problem of heterocedasticity?

Not based on that information. Try the following instead:

fit <- lm(y~g)
par(mfrow=c(2,2)); plot(fit)

-- 
   O__  ---- Peter Dalgaard             ุster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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Received on Thu Aug 03 23:51:35 2006

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