From: Chuck Cleland <ccleland_at_optonline.net>

Date: Thu, 06 Mar 2008 05:03:42 -0500

>> 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.
*

Date: Thu, 06 Mar 2008 05:03:42 -0500

On 3/5/2008 3:19 PM, jebyrnes wrote:

> 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.

-- Chuck Cleland, Ph.D. NDRI, Inc. 71 West 23rd Street, 8th floor New York, NY 10010 tel: (212) 845-4495 (Tu, Th) tel: (732) 512-0171 (M, W, F) fax: (917) 438-0894 ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.Received on Thu 06 Mar 2008 - 10:15:23 GMT

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