A simple type of hypothesis test. Denote the value of some test statistic by T. The observed data values are randomly redistributed amongst the experimental units. The test statistic is calculated for each such redistribution. Depending on the number of data values, either all possible permutations are made, or a random selection (of say 1 000 permutations) is made. For each permutation the value of the test statistic is considered. The significance of the value T is determined by the proportion of permutations that lead to values greater than, or equal to, T.