[R] Levene's test
maj at waikato.ac.nz
Fri Sep 1 06:32:24 CEST 2000
I'm teaching one-way anova at the moment and throwing in a few snippets of
R on the way. I'd like to present a modified version of Levene's test for
homogeneity of variance between groups and give some R code for it.
The test that I was thinking of basically does an anova on a modified
response variable that is the absolute value of the difference between an
observation and the median of its group (more robust than Levene's original
choice, the mean).
A colleague has suggested an approach involving the functions
ord() split() sapply() as.vector() rep()
which I have not quite got working yet. Even if I do get it working it
seems to make fairly heavy weather of would I would have thought was a
simple enough transformation. I'd like something that I could show my
students without discouraging them!
Suggestions gratefully received!
Murray Jorgensen, Department of Statistics, U of Waikato, Hamilton, NZ
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