Friedman Test

In an attempt to control for unwanted variability, researchers often implement designs that pair or group participants into subsets based on common [Page 511]characteristics (e.g., randomized block design) or implement designs that observe the same participant across a series of conditions (e.g., repeated-measures design). The analysis of variance (ANOVA) is a common statistical method used to analyze data from a randomized block or repeated-measures design. However, the assumption of normality that underlies ANOVA is often violated, or the scale of measurement for the dependent variable is ordinal-level, hindering the use of ANOVA. To address this situation, economist Milton Friedman developed a statistical test based on ranks that may be applied to data from randomized block or repeated measures designs where the purpose is to detect ...