Math

T-Test Calculator

Compare two sample means and get t statistic and p-value instantly

Enter two datasets to compare their means.

How This T-Test Calculator Works

This calculator runs Welch's two-sample t-test, which compares the means of two independent samples without assuming equal variances. Paste one dataset into Sample A, another into Sample B, choose the tail type, and the tool calculates the t statistic, Satterthwaite degrees of freedom, p-value, and mean difference instantly.

Welch's T-Test Formula

The test statistic is t = (x̄1 - x̄2) / sqrt(s12/n1 + s22/n2). Unlike the pooled t-test, Welch's version adjusts the degrees of freedom using the sample variances and sizes from both groups.

How To Interpret The Output

Focus on three outputs together: the mean difference tells you the direction and size of the gap, the t statistic shows how large that gap is relative to sampling noise, and the p-value tells you whether the result is statistically significant at your chosen confidence level.

Frequently Asked Questions

When should I use Welch's t-test?
Use Welch's t-test when you are comparing the means of two independent samples and you do not want to assume equal variances. It is a safer default than the pooled two-sample t-test.
What does the p-value mean here?
The p-value is the probability of seeing a mean difference at least this extreme if the true population means were equal. Smaller p-values indicate stronger evidence against the null hypothesis.
What is the difference between one-tailed and two-tailed tests?
A two-tailed test checks for any difference in either direction. A left-tailed test checks whether Sample A is smaller than Sample B. A right-tailed test checks whether Sample A is larger than Sample B.
How many values do I need?
Each sample needs at least two numeric values. In practice, larger samples give more stable variance estimates and more reliable inference.

Related Tools

ANOVA Calculator
Compare three or more groups and test for mean differences
Normal Distribution Calculator
Find z-scores, PDF, CDF, and interval probabilities instantly
Chi-Square Calculator
Test categorical counts for fit or independence in seconds