# Definition

The Fisher’s test is used to** compare two proportions **from two independent groups. It helps to conclude if there seems to be an association between two factors or two diseases or a factor and a disease. It is used when the Chi² test cannot be performed because of too small samples.

# In practice

If there is** less than 5 patients for at least one case** of a contingency table, as :

Tobacco / COPD | COPD positive | COPD negative |

Smoker | 50 | 2 |

No smoker | 5 | 50 |

The Chi² test will be replaced by the Fisher's test.

# How to use it on EasyMedStat ?

- Go to Statistics > Test variables
- Select a first variable which could be of types Yes-no or List
- Select a second variable which could be of types Yes-no or List
- Click on "Find a statistical association between ..."

If your samples are large enough, a chi-squared test will be performed automatically.