Hi
On 28 Nov 1999, Donald F. Burrill wrote:
> On Sun, 28 Nov 1999, Rich Ulrich wrote in part:
> > This is consistent with what Donald says, about the appearance of cell
> > means being disordinal once you have subtracted out the main effects
> > (so, why would you want to do that?).
>
> Most of the time, I wouldn't. Displays of the cell means, with main
> effects and interactions all present and accounted for, are often much
> more evocative of useful interpretation, in my experience.
> But the idea of "interaction" was defined, when the world was
> young and I was learning some statistics, as the systematic differences
> among cells that remained after you'd removed the main effects; and in
> part I was merely pointing out that what most people actually plot is not
> that, but the several cell means whose interpretation is at issue...
I too prefer the actual means, but some people (e.g., Rosenthal)
have argued strongly that the residual means should in fact be
reported to demonstrate the nature of the interaction.
Best wishes
Jim
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James M. Clark (204) 786-9757
Department of Psychology (204) 774-4134 Fax
University of Winnipeg 4L05D
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