On Feb 1, 2012, at 4:34 PM, Mark Na wrote:
Dear R-helpers, I have an ANCOVA with a significant effect of the factor, which has three levels. I wish to determine which of the levels are different from each other but, because my model was fitted with lm(), I cannot use TukeyHSD. For some reason, I get different results (no significant effect of the factor) when I fit the model using aov()
... which is just a wrapper to "lm" ...'
so, for the moment, I am using lm().
Doesn't that seem to violate a common sense rule? You should not pick a test (or in this test one particular formulation to the same function) just because it gives you the answer you want, but rather because it is appropriate for your data situation.
Could anyone point me to a test and associated R function that will work on a fitted lm() or glm()?
Given what little you have said about your design and data analysis program, and what sort of heuristics you seem to use for choosing your tests, it seems that it might be unwise to give suggestions.
-- David Winsemius, MD West Hartford, CT ______________________________________________ R-help@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.
