On 06/17/2010 07:12 PM, David Winsemius wrote:
On Jun 16, 2010, at 1:43 PM, Tal Galili wrote:
Hello Jeremy,
Thank you for replying.
I came across friedman test (I even wrote and published R code to easily
perform a post-hoc analysis of friedman
test<http://www.r-statistics.com/2010/02/post-hoc-analysis-for-friedmans-test-r-code/>
).
But what I am after is *multi-way* repeated-measures anova. Thank you for
your reply which allowed me to clarify my intentions.
Many years ago I remember reading advice in Conover and Iman's
"Practical Non-Parametric Statistics" that one could apply a rank
transformation to the dependent and independent variables and then run a
typical anova test. This is probably inferior in many ways to doing
quantile regression (don't know if this has a repeated measures
extension) or to the use of robust standard errors for examining
inferential issues in regression models, but it certainly represents a
useful consistency check when all you are worried about is influential
points in a skew distributions. I cannot comment on how it would
theoretically behave in a repeated-measures analysis, but I suspect that
there are readers of this list who can comment with greater authority,
and I invite them to do so.
David - the rank transform method doesn't handle interactions properly,
among other problems. The proportional odds model is the logical
extension of the Wilcoxon-Kruskal-Wallis approach. It relies only on
the rank of Y and reduces to the regular nonparametric tests as special
cases.
Frank
--
Frank E Harrell Jr Professor and Chairman School of Medicine
Department of Biostatistics Vanderbilt University
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