Friedman test
时间: 2024-06-06 08:07:52 浏览: 17
The Friedman test is a non-parametric statistical test used to compare the differences among three or more groups of related or matched samples. It is used when the data are not normally distributed and/or when the assumptions of a parametric test, such as ANOVA, are not met.
The Friedman test ranks the data within each group, and then calculates the sum of ranks for each group. The test statistic is calculated based on the differences between the ranks of each group, and it is compared to a chi-square distribution with degrees of freedom equal to the number of groups minus one.
If the p-value is less than the significance level, we can conclude that there is a significant difference between the groups. However, the Friedman test does not tell us which groups differ significantly from each other. Therefore, if we find a significant difference, we need to perform post-hoc tests, such as the Wilcoxon signed-rank test, to identify the specific group differences.