Independent Samples T-test
A variation of the t-test used to compare the means of two independent, mutually exclusive groups.
What is Independent Samples T-test?
The independent-samples t-test evaluates whether the means of two completely separate groups differ significantly. It assumes that the observations in one group are entirely independent of the observations in the other group, and typically assumes that both groups have similar variances (homogeneity of variance).
Why Independent Samples T-test Matters
It is the standard method for determining if a between-subjects experimental manipulation (like treatment vs. control) caused a difference, or if two distinct subpopulations differ on a continuous metric.
Example
An education researcher uses an independent-samples t-test to compare the final exam scores of students who attended a traditional lecture class against those who attended an online-only class.
Common Mistakes
- Applying this test when the two groups are related or matched (e.g., pre-test/post-test on the same people).
- Failing to check for or correct for unequal variances between the two groups (e.g., failing to use Welch's t-test when appropriate).