Dear all,
I want to study the global effect of Age (with three levels) over the GM volumen. So, I thought to perform an one-way ANOVA using the following F-contrast:
[1 -1 0 ; 0 1 -1]
Is it actually correct? Beacuse these two contrast vectors are non-orthogonal, whereas typical ANOVA's would use a full set of orthogonal contrasts to divide the "treatment" SS, e.g. [1 -1 0; 1 1 -2].
My second question is, if this F-contrast is definitely correct and I obtain a significant effect of Age, then I try to evaluate the following post-hoc contrasts:
[1 -1 0] [1 0 -1] [0 1 -1]
and the reverse contrasts:
[-1 1 0] [-1 0 -1] [0 -1 1]
So, how should I correct these multiple comparisons in order to avoid the type 1 error.
Thank you very much in advance
Daniel Ferreira
|