What this calculator does
F-test for equal variances works out compares the spread of two samples using the ratio of their variances. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaF = s₁² / s₂², using the larger variance on top; df₁ = n₁−1, df₂ = n₂−1
The inputs explained
| Field | What to enter |
|---|---|
| Sample 1 standard deviation | A number. Starts at 12. |
| Sample 1 size | A number. Starts at 15. |
| Sample 2 standard deviation | A number. Starts at 7. |
| Sample 2 size | A number. Starts at 20. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with sample 1 standard deviation
Every other input is held at the calculator’s starting values while sample 1 standard deviation varies. Select any row to load that scenario into the calculator.