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SPSS Output Explorer
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Paired-samples t-test
Do students' test-anxiety scores change between before and after a four-week, self-paced study-skills workshop? 25 students completed the same questionnaire at both time points.
Only the parts of the output needed to read this result are shown. Where SPSS prints more, a note under the table says what has been left out and why.
| Mean | N | Std. Deviation | Std. Error Mean | ||
|---|---|---|---|---|---|
| Pair 1 | Pre-workshop anxiety | 25 | 1.120 | ||
| Post-workshop anxiety | 25 | 1.420 | |||
| N | Correlation | Significance | |||
|---|---|---|---|---|---|
| One-Sided p | Two-Sided p | ||||
| Pair 1 | Pre-workshop anxiety & Post-workshop anxiety | 25 | <.001 | ||
| Paired Differences | t | df | Significance | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mean | Std. Deviation | Std. Error Mean | 95% Confidence Interval of the Difference | |||||||
| Lower | Upper | One-Sided p | Two-Sided p | |||||||
| Pair 1 | Pre-workshop anxiety - Post-workshop anxiety | 1.131 | ||||||||
| Standardizer | Point Estimate | |||
|---|---|---|---|---|
| Pair 1 | Pre-workshop anxiety - Post-workshop anxiety | Cohen's d | 5.656 | |
The Standardizer is the denominator used to estimate the effect size. For paired data, Cohen's d uses the standard deviation of the differences.
Selected output. Not shown: the 95% confidence interval columns and the Hedges' correction row. SPSS prints these, but its calculation methods for them have not yet been independently confirmed, so they are left out rather than risk showing an incorrect value.
About this example
25 students completed the same test-anxiety questionnaire before a four-week, self-paced study-skills workshop and again four weeks later. Each student completed the workshop on their own. The questionnaire has 10 items rated 1 to 5 (total 10 to 50; higher scores mean more anxiety). Each student contributes one pair of scores, and the differences are calculated as Pre − Post.
Limitations
- The data are simulated for teaching.
- There was no control group. The change could reflect time passing, the approach of exams, regression to the mean or familiarity with the questionnaire, not only the workshop.
- Test anxiety is self-reported.
- The sample is small (25 students), so the mean change is estimated imprecisely.
- The total of a rating scale is treated as approximately continuous.
What can be concluded
The results show that test-anxiety scores were lower, on average, four weeks after the workshop than before it, and that this change is statistically significant. Because there was no control group, they do not show that the workshop caused the change. Report the result cautiously: describe the direction of the change, say whether it is statistically significant, and give the effect size and confidence interval.
Working on your own paired-samples t-test?
This Explorer is a free teaching resource. Its examples use simulated data, and it does not run analyses or look at your own output.
The Result Decoder (paid) is for your own results: you enter the values from your completed analysis and get an APA 7 results paragraph, a plain-English interpretation, checks on the values you entered, effect-size guidance, charts where available and Defend This Result practice.
Free guide: How to Report a Paired-Samples t-Test in APA 7