What is the difference between one-tailed and two-tailed Fisher's exact test?

A one-tailed test checks for an association in a specific direction, while a two-tailed test evaluates whether any association exists regardless of direction. The two-tailed p-value is typically larger and more conservative.

When should I use Fisher's exact test instead of a chi-squared test?

Fisher's exact test is preferred when sample sizes are small, or when one or more cells in the 2x2 table have expected counts below 5, as chi-squared relies on approximations that may be inaccurate in these cases.

Can I use this calculator for tables larger than 2x2?

No, this specific tool is built for 2x2 contingency tables only. For larger tables, other exact tests or software packages designed for multi-way tables would be required.

What does the odds ratio value indicate in the results?

The odds ratio quantifies the strength of the association between the two variables; a value of 1 indicates no association, while values greater than or less than 1 indicate the direction and magnitude of the association.

StatisticsFree Tool

Fisher's Exact Test Calculator

Provided byOmni Calculatoromnicalculator.com

The Fisher's exact test calculator performs a one-tailed and two-tailed Fisher's test on any given 2 x 2 contingency ...

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Inference, regression, and statistical tests calculators

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About this tool

What Fisher's Exact Test Calculator does

This tool evaluates whether there is a statistically significant association between two categorical variables by running Fisher's exact test on a 2x2 contingency table. Users input the cell counts (a, b, c, d) and receive both one-tailed and two-tailed p-values, along with the odds ratio as a measure of effect size. The output is designed for quick interpretation of statistical significance in small sample scenarios where chi-squared approximations may be unreliable.

Step by step

How to use the Omni Calculator Fisher's Exact Test Calculator

1
Enter the count for cell a in the top-left of the 2x2 table
2
Enter the count for cell b in the top-right
3
Enter the count for cell c in the bottom-left
4
Enter the count for cell d in the bottom-right
5
Select the test type (one-tailed or two-tailed) and view the resulting p-value and odds ratio below the table

Is it right for you

Best for

Researchers, students, or analysts working with small sample sizes who need to test the independence of two dichotomous variables without relying on asymptotic approximations.

Limitations

Designed specifically for 2x2 tables; larger contingency tables require different methods
Input values must be non-negative integers; decimal or negative entries are not supported
Provides p-values and odds ratios but does not interpret practical significance or context-specific meaning

Questions

Fisher's Exact Test Calculator FAQ

What is the difference between one-tailed and two-tailed Fisher's exact test?: A one-tailed test checks for an association in a specific direction, while a two-tailed test evaluates whether any association exists regardless of direction. The two-tailed p-value is typically larger and more conservative.
When should I use Fisher's exact test instead of a chi-squared test?: Fisher's exact test is preferred when sample sizes are small, or when one or more cells in the 2x2 table have expected counts below 5, as chi-squared relies on approximations that may be inaccurate in these cases.
Can I use this calculator for tables larger than 2x2?: No, this specific tool is built for 2x2 contingency tables only. For larger tables, other exact tests or software packages designed for multi-way tables would be required.
What does the odds ratio value indicate in the results?: The odds ratio quantifies the strength of the association between the two variables; a value of 1 indicates no association, while values greater than or less than 1 indicate the direction and magnitude of the association.

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