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Compare two groups and get an exact p-value in seconds. Paste your numbers, and the calculator picks the right test - Student's t-test, Welch's t-test, or the Mann-Whitney U test - then hands you a paste-ready methods sentence for your paper.
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A two-sample (unpaired) t-test asks whether the means of two independent groups differ by more than you would expect from random sampling. Enter each group's measurements, choose Auto-pick, and the calculator validates the test's assumptions for you before reporting the p-value.
A p-value below 0.05 is the conventional threshold for "statistically significant," meaning the observed difference is unlikely under the null hypothesis of no difference. The calculator also reports significance stars (* p<0.05, ** p<0.01, *** p<0.001) so the result drops straight onto a figure.
When a group is small or clearly non-normal, the parametric t-test can mislead. In that case the Mann-Whitney U test compares the distributions using ranks instead of means and makes no normality assumption. Auto-pick switches to it automatically when the Shapiro-Wilk check fails. Comparing three or more groups instead? Use the ANOVA calculator.
On Auto-pick, the calculator checks normality (Shapiro-Wilk) and equal variance (Levene). If both groups are approximately normal with equal variances it runs a Student's t-test; if variances differ it runs Welch's t-test; if a group is not normal (or too small to judge) it runs the non-parametric Mann-Whitney U test. You can also force a specific test.
Both compare two means, but Student's t-test assumes the two groups have equal variances while Welch's t-test does not. Welch's is the safer default when group sizes or spreads differ, which is why the auto-picker selects it when Levene's test flags unequal variance.
Your numbers are sent to Plotivy's compute service to run the test with scipy and are not stored. Nothing is saved to an account because no sign-up is required.
Copy the generated methods sentence, which names the test, the per-group sample sizes, and the error-bar convention. Pair it with the p-value and the group means shown in the descriptives table.
Compare two groups (Student's, Welch's, or Mann-Whitney).
Compare three or more groups with Tukey post-hoc.
Pearson or Spearman matrix with APA, LaTeX & CSV export.
OLS coefficients, betas, R-squared and F in an APA table.
In-depth guide to running these tests in code.
Plotivy runs the test, picks the right chart, and annotates significance bars on a publication-ready figure - all from your data.
Open the Analyze tool