How to use the T-Test Calculator
- 1. Choose the testPick independent groups, paired data or one sample against a value.
- 2. Paste your dataEnter the raw values for each group.
- 3. Read the decisionSee t, df, p-value and whether the difference is significant.
Which t-test to use
- Welch two-sample: two separate groups, such as two batches of students. Does not assume equal variances. The safe default.
- Pooled two-sample: the classic Student's t-test. Only use it if the group variances are similar.
- Paired: the same people measured twice, such as before and after training. It tests the differences.
- One-sample: one group against a target value, such as mean delivery time vs a 30-minute promise.
Worked example and formula
Welch's statistic is t = (x̄₁ − x̄₂) ÷ √(s₁²/n₁ + s₂²/n₂), with degrees of freedom from the Welch–Satterthwaite formula. In the default data, batch A (8 students) averages 86.625 and batch B averages 77.625. Their SDs are 6.6319 and 5.0409, so t = 3.0558 with about 13.06 df, and the two-sided p-value is 0.0092. That is below 0.05, so the difference is statistically significant. The 95% interval for the gap runs from about 2.64 to 15.36 marks.
The p-value comes from the t-distribution itself, so results match SciPy's ttest_ind(a, b, equal_var=False). A significant result does not mean a big or important difference; look at the interval too. T-tests assume roughly normal data in each group, which matters most for very small samples with strong skew. For categories instead of numbers, use the chi-square calculator.
Frequently asked questions
What does a one-sided test do?
It only looks for a difference in one direction, such as A being greater. Use it only if you decided the direction before seeing the data.
Can I enter means and SDs instead of raw data?
Not on this page. It needs the raw values so it can check the data and compute everything consistently.
Is the T-Test Calculator free?
Yes, the T-Test Calculator is free. The first time you see your first result, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.