T-Test for 2 Independent Means

Method overview

When to use

Use when two unrelated groups are measured on a continuous outcome, such as treatment vs control or male vs female.

Input requirements

Enter two numeric vectors. Values can be separated by commas, spaces, tabs, or new lines. Each group needs at least 2 values.

Key assumptions

• Two independent samples.
• The outcome is approximately normally distributed within groups, especially for small samples.
• Use Welch t-test when equal variance is not assumed.

Null hypothesis

H₀: the two population means are equal, μ₁ − μ₂ = 0.

Method used

Welch t-test or Student equal-variance t-test; P value from the t distribution.

References

• Student. The probable error of a mean. Biometrika, 1908.
• Welch BL. The generalization of Student’s problem. Biometrika, 1947.