Paired Samples t Test Calculator

The paired samples t test (also called the dependent or repeated-measures t test) compares two measurements taken from the same participants, such as pre-test and post-test scores after a training programme. Paste the two columns and get the mean difference, its 95% confidence interval, t, p, Cohen’s d_z and an APA 7 paragraph.

How to use this calculator

  1. Put the first measurement (e.g. Pre) in one column and the second (e.g. Post) in the next. Each row must be the same participant.
  2. Copy both columns, with or without headers, and paste them.
  3. Click Calculate.
  4. Read the Paired Samples Test table and copy the APA paragraph.

Formula

dᵢ = x₁ᵢ − x₂ᵢ (difference for each participant)
t = d̄ / (s_d / √n),  df = n − 1
Cohen's d_z = d̄ / s_d

Step-by-step example

  1. Ten students: Pre M = 64.70, SD = 6.13; Post M = 68.60, SD = 5.46.
  2. Mean difference d̄ = -3.90, SD of differences = 2.470.
  3. SE = 2.470 / √10 = 0.781.
  4. t(9) = -3.90 / 0.781 = -4.99, p = .001, d_z = -1.58.

How to interpret the results

A p-value below .05 means the average change between the two measurements is statistically significant. A negative t here means scores increased from Pre to Post (Pre minus Post is negative). The confidence interval of the mean difference shows the likely size of the change; d_z expresses it in standard-deviation units.

How to report it in APA 7 style

A paired-samples t test showed that scores increased significantly from the pre-test (M = 64.70, SD = 6.13) to the post-test (M = 68.60, SD = 5.46), t(9) = -4.99, p = .001, d = -1.58.

Statistical symbols (t, F, p, r, M, SD, N, d) should be italicised in your thesis.

Assumptions

  • The dependent variable is continuous.
  • The two measurements come from the same participants (or matched pairs).
  • The differences are approximately normally distributed.
  • No extreme outliers in the differences.

How to do it in SPSS, R or Excel

SPSS: Analyze → Compare Means → Paired-Samples T Test. R: t.test(pre, post, paired = TRUE). Excel: =T.TEST(pre, post, 2, 1).

Roman Urdu mein khulasa

Paired t test aik hi logon ke do measurements compare karta hai, jaise training se pehle aur baad ke marks. Excel mein pehla column Pre aur dusra Post rakhein, aur har row usi student ki ho. p 0.05 se kam ho to change significant hai. Agar t negative aaye to iska matlab hai ke Post ke marks Pre se zyada hain.

Frequently asked questions

What is the difference between a paired and an independent t test?

A paired t test compares two measurements from the same people (or matched pairs). An independent t test compares two different groups of people.

What if I have missing values in one column?

Each row must contain both measurements. Remove participants with a missing pre or post score before pasting, otherwise the calculator will ask you to make the columns equal.

What is Cohen’s d_z?

d_z is the mean difference divided by the standard deviation of the differences. It is the standard effect size for paired designs and is what G*Power uses for paired-samples power analysis.

What if the differences are not normal?

For small samples with clearly non-normal differences, use the Wilcoxon signed-rank test instead.

Can I use this for more than two time points?

No. For three or more measurements of the same people, use a repeated-measures ANOVA.

How do I report a paired t test in APA?

Give both means and SDs, then t(df) = value, p = value, and the effect size, e.g. t(9) = −4.99, p < .001, d = −1.58.

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Cite this calculator

If ScholarCalc helped your analysis, you can cite it in APA 7 format:

ScholarCalc. (2026). Paired Samples t Test Calculator [Web application]. https://scholarcalc.com/paired-t-test-calculator/

Written and maintained by the ScholarCalc team. Last reviewed: November 2026.

Accuracy: results are computed in your browser and were validated against Python scipy, statsmodels and pingouin on test datasets. See Methodology and accuracy.