One-Way ANOVA Calculator

Compare three or more group means at once — get the F-statistic, degrees of freedom, p-value, and effect size.

Your groups

Group 1

Group 2

Group 3

F-statistic

29.6

2, 9

p-value

0.00011

Group means: 13.5, 17.5, 10.5

η² (eta-squared) = 0.868 — 86.8% of variance explained by group membership.

At α = 0.05, this result is statistically significant (p < 0.05) — reject H₀. At least one group mean differs.

Formula Reference

F-statistic

F = MSbetween / MSwithin

Effect size

η² = SSbetween / SStotal

Calct-Test Calculator ArticleOne-Way ANOVA: Full Worked Example ArticleHypothesis Testing Framework

Frequently Asked Questions

What does a significant ANOVA result actually tell me?+

Only that at least one group mean differs from the others — not which one, or how many. Identifying which specific groups differ requires a follow-up post-hoc test like Tukey's HSD, which correctly controls the error rate across multiple pairwise comparisons.

Why not just run separate t-tests between each pair of groups?+

Running multiple pairwise t-tests inflates the overall false-positive rate well beyond the stated significance level, since each test carries its own risk and those risks compound. ANOVA tests all groups at once with a single, correctly-calibrated error rate.

What does η² (eta-squared) tell me?+

The proportion of total variance explained by group membership, from 0 to 1. Conventional benchmarks: around 0.01 is a small effect, 0.06 medium, 0.14 large — though these vary by field.

How many groups can I enter?+

This calculator supports as many groups as you add data for — at least 2 are required, though ANOVA is really designed for 3 or more (with exactly 2 groups, it gives the same result as an independent two-sample t-test).