T-Test Calculator
Quick t-test hub: paste two columns of data (or one column for a one-sample test) and get t, df, p-value, mean difference, confidence interval, and effect size.
Default here: independent samples with a pooled variance t-test (matches many textbooks). Welch, paired, and one-sample modes are one click away. Deeper options: two-sample t-test, paired t-test, one-sample t-test, degrees of freedom. Nonparametric: Mann–Whitney U.
Numbers separated by commas or spaces.
Numbers separated by commas or spaces.
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Worked example (Load example)
Group 1: 5, 6, 7, 8, 9 and Group 2: 3, 4, 5, 6, 7 with the default pooled independent test give mean difference 2, t = 2, df = 8, two-sided p ≈ 0.0805.
Honest default note
This hub defaults to the pooled two-sample t-test so results align with older textbooks and TI-84 pooled settings. Many software packages default to Welch instead; use the Welch test type here or the two-sample calculator for summary-statistics input and side-by-side comparison.
Frequently Asked Questions
Should I use independent or paired?
Independent when groups are different people; paired when the same units are measured twice or naturally matched.
Why is pooled the default on this page?
To preserve the classic teaching workflow; switch to Welch if group SDs may differ (often the better modern choice).
Is the p-value one- or two-tailed?
Two-tailed by default on this hub (α split between both tails).
What does Mean Difference show for one-sample?
For one-sample it is x̄ − μ₀ (the numerator of the t statistic).
Where are confidence intervals and effect sizes?
Shown in the result grid after you calculate; specialized pages add more detail and one-sided options.
My p-value is just above 0.05: what now?
Report the exact p, the mean difference, and CI; consider whether a larger study is needed.
Can I share my inputs?
Use Copy link: it encodes group data and test type in the URL.
What if assumptions fail?
Try Welch for unequal variances, check normality on differences or within groups, or use Mann–Whitney / Wilcoxon links above.
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