Message-ID: <15857771.post@talk.nabble.com>
Date: 2008-03-05T20:19:22Z
From: Jarrett Byrnes
Subject: Asking, are simple effects different from 0
In-Reply-To: <47CEEB60.40200@optonline.net>
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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