Overview of Friedman's test and post-hoc analysis

Abstract

When the null hypothesis of Friedman's test is rejected, there is a wide variety of multiple comparisons that can be used to determine which treatments di er from each other. We will discuss the contexts where di erent multiple comparisons should be applied, when the population follows some discrete distributions commonly used to model count data in biological and ecological elds. Our simulation study shows that sign test is very conservative. Fisher's LSD and Tukey's HSD tests computed with ranks are the most liberal. Theoretical considerations are illustrated with data of Azores Buzzard (Buteo buteo rothschildi) population from Azores, Portugal.