Fisher's Exact Test: what it means and how to read it
In the report: Fisher's Exact Test — The exact p of a 2 × 2 table, in the two Exact Sig. columns; the value, df and asymptotic columns are empty. The row is absent for larger tables.
How to read it
Use it instead of Pearson when the table is 2 × 2 and some expected counts are below 5 (Warnings says so): it does not rest on a large sample.
In plain words
A small clinic asked 12 people to try either a new or an old stretching routine and then say whether their back felt better, yes or no. With so few people, the usual test gives a shaky answer. The clinic looked at Fisher's Exact Test instead and got 0.03. That means only about 3 times in 100 would so lopsided a table show up by luck alone, so it is hard to put down to chance alone. If such a table came by luck 40 times in 100, it could easily be luck. Now the clinic can give an honest answer even with only 12 people.
How it is computed
2-sided: the sum of the probabilities of all tables with the same totals that are not more probable than the observed one.1-sided: the probability of the observed table and of the more extreme ones in the direction of the relation seen.Where you see it
STATS_CHI2— Pearson chi-square test for association between two categorical columns.
Related values
- Linear-by-Linear Association — The test of a linear trend between the codes of the two columns, df = 1. Shown only when both columns have codes: numbers, or labels with numbers; text without labels has no such row, as in SPSS.
- F statistic — A ratio of two variance estimates. The larger F, the stronger the evidence against the null hypothesis; its p comes from the F distribution with the two degrees of freedom next to it.
- Degrees of freedom between groups — The first degrees of freedom of F: the number of groups minus 1.
- Degrees of freedom within groups — The second degrees of freedom of F. For the classic test — all values minus the number of groups; for Welch it is smaller and usually fractional.
- Degrees of freedom 1 — The first (numerator) degrees of freedom of the F statistic next to it.
Get it in your sheet
One formula in a cell gives the whole report, Fisher's Exact Test included. ALS Stats is a free add-on for Google Sheets™.
Install ALS Stats from Google Workspace Marketplace (opens in a new tab)