GLM with non-parametric post hoc testing?

mayia

New Member
#1
Hi guys,
I have a question regarding the appropriate use of comparisons for independent samples (3 factor levels), please.
Overall sample size is N=546, subsamples: 218 or 228 or 100), convenience sampling, stratified.
I use ANOVA with post hoc Tukey, if Levene indicates variance homogeneity.
My question:
If there no equal variance: What do do?
a) Using Kruskal-Wallis?
> For post hoc: Do I use Mann-Whitney for pairwise comparisons (if so: what about the alpha inflation?)?
b) Still using GLM but with non-parametric post hocs?
> If so: which one? Tamhane? Dunnett or Games-Howelll?
> What about F, can I still use it? isn’t H then the more appropriate statistic?
> Why gives GLM anyway the option of running on-parametric tests of homoscedasticity is an assumption (am confused ;-( )

Thanks for any input on this one ☺
 

hlsmith

Less is more. Stay pure. Stay poor.
#2
So in your overall GLM model, do you have homoscedasticity of residuals? If not, on options may be using Kruskal Wallis followed by Mann-Whitney.