Happy New Year all.
I've been running a regression analysis of a whole sample and now want
to examine the sample by group.
I'm using Factorial Anova to assess why the groups differ. Until now the
sample size was large and I had no issues with homogeneity of variance.
Now the total sample of 198 is broken down into six groups of roughly
equal sizes.
Levene's Test is significant when doing Factorial ANOVA.
The first advice of Andy Field on this is to go back and transform data.
However SPSS (16) won't produce a Levene's Test with transformed data
because it warns of 'non positive values'.
This was understandable when I was using centred data (which I'd needed
for earlier analysis and continued using without thinking) but not when
I reverted to non centred data, none of which has any negative values in
any of the columns.
I've tried each form of transformation offered by SPSS without success.
Has anyone got any advice over what is going on and what I might do
next?
Many thanks.
Caroline Wilson
PhD student
De Montfort University
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