[R-sig-ME] p values for factor effect in lmer
Jonathan Baron
baron at psych.upenn.edu
Thu Dec 13 18:45:37 CET 2007
Suppose I have something like
l1 <- lmer(y ~ x + f + (1 | s))
where f is a factor with levels 1, 2, 3.
l1 itself lists the individual values, f1, f2, f3, not the overall
effect of f.
anova(l1) gives the overall effect of f, but no p values.
pvals.fnc(l1) from the languageR package is like l1 itself. But I
want to know whether the factor has a significant effect.
I could do
l2 <- lmer(y ~ x + (1 | s))
anova(l1,l2)
but, in my experience so far, this method gives answers that don't
look right and don't agree with other methods. I have not been
trusting it to provide p values. pvals.fnc(), by contrast, usually
gives very sensible values that agree with other approaches.
Can anyone suggest another approach? ("Wait until the next version of
..." is a legitimate answer, if it is true.)
Or maybe I should trust anova(l1,l2) after all.
Jon
--
Jonathan Baron, Professor of Psychology, University of Pennsylvania
Home page: http://www.sas.upenn.edu/~baron
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