Categorical Data Analysis Using The SAS® System, 2nd Edition

7.4. Friedman’s Chi-Square Test

Friedman’s test (1937) is a nonparametric method for analyzing a randomized complete block design. This type of study design is applicable when interest is focused on one particular factor, but there are other factors whose effects you want to control. The experimental units are first divided into blocks (groups) in such a way that units within a block are relatively homogeneous. The size of each block is equal to the number of treatments or conditions under study. The treatments are then assigned at random to the experimental units within each block so that each treatment is given once and only once per block. The basic design principle is to partition the experimental units in such a way that background variability ...