means
Welch's t-test
Compare a continuous outcome between exactly two independent groups without assuming equal variances.
Requirements
- continuous outcome
- one two-level group
- independent observations
Avoid when
- paired/repeated observations
- three or more groups
- strong ordinal/non-normal outcome with small n
Formula
t = (x̄₁ − x̄₂) / √(s₁²/n₁ + s₂²/n₂)
Interpretation
Reports the mean difference, t statistic, p-value, and confidence interval.
Worked example
Compare mean blood pressure between two independent treatments with unequal variances.
Open example datasets