# MASH : Maths and Stats Help

### Paired Samples t-Test

#### Introduction

A Paired-Samples t-Test compares the means between two related groups, such as comparing the difference between pre-intervention and post-intervention test results.

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

If your data is non-parametric you should consider using a Wilcoxon Test.

#### Test Procedure

1. Click Analyze > Compare Means > Paired-Samples T Test 2. Within the Paired Samples t-Test box, select the two variables you wish to analyse and move to them to the Paired Variables Box using the right arrow 3. Click OK

#### Results

SPSS will generate three tables, for this test we need two, the Paired Samples Statistics and the Paired Samples Test. ##### Paired Samples Statistics

This table shows a selection of descriptive statistics: the sample size of each group (N), the mean of each group (Mean), and the standard deviation of each group (Std. Deviation), best practice is to report them all.

##### Paired Samples Test

This table shows the specific test results including the t-statistic (t), the degrees of freedom (df) the two-tailed significance or p-value (Two-Sided p), and the 95% Confidence Interval (95% Confidence Interval of the Difference).

## Reporting the Results in APA Formatting

Students’ test results were compared before and after the intervention. On average, students performed better (M = 73.30, SD = 11.91) after the intervention than before (= 69.00, SD = 6.64). A Paired-Samples t-Test indicated this difference, d̄ = 4.30, 95%CI [0.83, 7.77] was statistically significant, (19) = 2.60, = .018.