Asking, are simple effects different from 0
Indeed, but are not each of the cell means also evaluations of the effect of one factor at the specific level of another factor? Is this an issue of "Tomato, tomahto". I guess my question is, if I want to know if each of those is different from 0, then should I use the 48df from the full model, or the 9 for each cell?
Chuck Cleland wrote:
That does not corresponds to what I think of as the simple effects. That specifies the six cell means, but it does not *compare* any cell means. I think of a simple effect as the effect of one factor at a specific level of some other factor.
summary(glht(fm, linfct = cm2), test = adjusted(type="none")) Correct? What is the df on those t-tests then? Is it 48?
Yes, df = 48 for each contrast.
Interestingly, I find this produces results no different than fm2<-lm(breaks ~ tension:wool+0, data=warpbreaks) summary(fm2)
Yes, but those are not what I would call the simple effects. Those are essentially one-sample t-tests for each of the 6 cell means.
Also, here, it would seem each t-test was done with the full 48df. Hrm.
The df are based on the whole model, not the 9 observations in one cell.
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