T-Test Calculator
Run a two-sample t-test to compare the means of two groups.
Assumptions used in this calculation
- Equal variance assumed: Uses pooled-variance Student's t-test; results may differ from Welch's t-test for groups with very different variances.
About this calculator
Deciding whether two groups' averages are genuinely different, or just different by chance, is a common question in experiments and A/B comparisons, and answering it rigorously requires a t-test rather than simply comparing the two means directly, since that comparison alone says nothing about whether the gap is statistically meaningful. This calculator runs a two-sample, independent, equal-variance Student's t-test from each group's mean, standard deviation and sample size, computing t = (mean1 − mean2) ÷ √(pooledVariance × (1/n1 + 1/n2)), along with the degrees of freedom and the resulting p-value, the probability of seeing a difference this large if there were actually no real difference between the groups. It assumes both groups share equal population variances, the classic Student's t-test assumption; for groups with very different standard deviations, Welch's t-test would be more accurate. A common threshold is p < 0.05 to call a difference statistically significant. That replaces a comparison-by-eyeballing with a defensible statistical test.
Worked example
mean1=50 vs mean2=45
Result: t=1.75, p=0.085 (not significant)
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