# MASH : Maths and Stats Help

### Friedman's ANOVA

#### Introduction

A Friedman's ANOVA compares the difference between more than two related groups, such as comparing the difference between three time-points. If your data only has two groups such as a pre/post-test you should consider the Wilcoxon Test.

It is considered a non-parametric test and is suitable for non-parametric data. To check if your data is parametric, please check out the dedicated guide: Parametric or Not Guide (PDF)

If your data is parametric you should consider using a One-Way Repeated-Measures ANOVA

#### Test Procedure

1. Click Analyze > Nonparametric Tests > Legagy Dialogs > K Related Samples 2. Within the "Tests for Several Related Samples" Window, move your measurements into the "Test Variables" box. 3. Click "Statistics". Within the "Several Related Samples: Statisitcs", select 'Descriptives' and 'Quartiles'. 4. Select Continue à OK

#### Results SPSS will generate three tables, to correctly report this test we need two, the Descriptive Statistics and the Test Statistics:

##### Descriptive Statistics

This table shows the descriptive statistics: the sample size of each group (N), the mean of each group (Mean), and the standard deviation of each group (Std. Deviation). For non-parametric tests the most appropriate average would be the Median. You can get this out using the descriptive analysis in SPSS.

##### Test Statistics

This table shows the results of the statistics test including the sample size (N), the Chi-Square statistic (Chi-Square), the degrees of freedom (df), and the p-value/significance (Asymp. Sig.).

## Reporting the Results in APA Formatting

Samples were evaluated across three times (Week 1, Week 2, Week 3) using a Friedman's analysis of variance. Differences across the weeks were significant, χ2(2) = 22.76, p < .001.