ANOVA Calculator
Run a one-way ANOVA on three or more independent groups and see whether at least one group mean differs.
Why use this calculator
Compare multiple group averages in one test
A one-way analysis of variance (ANOVA) tests whether the variation between group means is larger than the variation within groups. It avoids running several unadjusted t-tests and inflating the chance of a false positive.
What does one-way ANOVA tell you?
ANOVA compares the spread of group means with the spread of values within groups. A small p-value is evidence that not all population means are equal. It does not tell you which group differs, how many groups differ, or whether the difference matters in practice.
The η² effect size estimates the share of total observed variation associated with group membership. Read it with the group means, metric units, and a decision threshold—not as a stand-alone verdict.
When to use ANOVA
Three or more independent groups
Use one-way ANOVA for one numeric outcome measured across independently assigned groups, such as control and several experiment variants. With only two groups, Welch’s t-test is usually more direct.
Plan the follow-up comparisons
After a significant omnibus test, use a suitable post-hoc procedure or pre-specified contrasts. Testing every pair at 5% without adjustment can substantially increase false positives.
Check the design, not only the formula
Observations should be independent, groups should have comparable variance for the classical model, and the metric should be defined consistently. Clustered assignment or highly skewed outcomes may need a different method.