Le nombre de permutations dans les tests permutationnels; The number of permutations in permutation tests

In a first part, the concepts and theory of exact randomization tests are reviewed, together with their implementation for each of a number of customary test situations including simple anova designs. Approximate (or incomplete) randomization tests are considered in the second part, as manageable alternatives to exact tests. We propose a model to calculate the relative power of approximate randomization tests and sketch out some guidelines for the user.