[R] Re Randomization test for interaction effect

Cliff Lunneborg cliff at ms.washington.edu
Fri Jul 22 02:18:50 CEST 2005

Dear Pedro,

How to test for an interaction--or, even, how to pose the question of an
interaction--in randomization-based inference is not at all obvious.
And, in the permutation test context reliance has been placed on the
exchangeability of (estimated) residuals under an additive,
homoscedastic model. Where estimated, the residuals are not exactly

A reference you might find useful is Pesarin, F (2001) "Multivariate
permutations tests." Wiley: Chichester, UK. His method of synchronized
permutations "may" be applied to test for interactions under some
limited circumstances.

Pedro de Barros writes, in part:

Dear All,

I am trying to build a randomization test for interaction

The problem is as follows: I have a set of stations where the occurrence
biomass of each species being investigated was recorded.


I would really appreciate any pointer to a solution of this problem. I
believe it is not complicated (and probably quite obvious) but the
keeps out of reach, even though I have been searching for over a week.


Cliff Lunneborg, Professor Emeritus, Statistics &
Psychology, University of Washington, Seattle
cliff at ms.washington.edu

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