[R] Anova with Scheffe Tests

From: Sam Ferguson <samferguson_at_ihug.com.au>
Date: Tue 01 Mar 2005 - 18:02:07 EST


Hi R-people,

I am wanting to run Factorial ANOVA followed by Scheffe tests on some spatial subjective data. I'm comparing X-Y independent coordinates against x-y dependent coordinates. There are only four independent spatial coordinates that form a square.

I am wondering whether I am doing the right thing, because there doesn't seem to be a simple way of doing this. I have attempted to read `Practical regression and ANOVA using R' and am still confused.

In good ol' Statview (now dearly departed) to complete a Scheffe test you selected the independent variables and dependent variable and it produced a table with the pairwise comparisons of the levels of the factor. I'm looking for a system that is as basic, but can be done using R and has documentation so I'm not guessing what I'm doing. I'd rather not have to do plots in R and then run over to dead software to do Scheffe's if possible.

I checked on google and there seems to be code for a couple of functions out there, but I need something that has a manual.

Is there a Scheffe function out there that is reasonably well documented, or should I consider some other method of dealing with this data. We have been using Scheffe for this type of analysis as I was under the impression it was very conservative. Tukey's HSD seems to be conservative as well. Should I try this? Is there a different approacch that is better and where can I read about it.

Thanks for any help you can provide.

Sam



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