Friedman Test

A common design in quantitative research involves the repeated testing of participants in a number of (k) different treatments or conditions. A related design involves the random allocation of subgroups of k matched individuals to k different treatments or conditions. In both cases, the observations are matched across the k conditions, and the research question is whether there is any variation among the conditions on some criterion variable. Classically, this question is addressed using an analysis of variance (with repeated measures in the former design and randomized blocks in the latter design). However, this procedure assumes that the criterion variable in question (a) is measured on an interval or ratio scale, (b) is normally distributed, and (c) has the same variance in all of the ...