t-Test Calculator

One-sample: compare one sample mean against a fixed hypothesised value.
Two-sample — pooled: compare two independent groups, assuming equal variances.
Two-sample — Welch: compare two independent groups without assuming equal variances — the safer default.
Paired: compare two measurements on the same subjects, e.g. before and after.

Runs a t-test on raw data: one-sample against a hypothesised mean, independent two-sample (pooled or Welch) or paired. Reports the test statistic, p-values, Cohen's d and a 95% confidence interval.