Fisher’s Exact Test – Learn It 2

  • Check the conditions for Fisher’s Exact Test
  • Explain the relationship of two qualitative binary variables using Fisher’s Exact Test

Fisher’s Exact Test

Fisher’s Exact Test (also known as Fisher’s Exact Test of Independence) is a statistical significance test used in the analysis of a [latex]2 \times 2[/latex] contingency table.

It is used to determine whether or not there is a significant association between two categorical variables.

Let’s revisit the motorcycle example.

A 2004 study titled “Motorcycle rider conspicuity and crash related injury: case-control study” looked at a similar context and, based on the conclusions of that study[1], the researcher decides to combine cells from the table below into a two-way table.

  Black helmet White helmet Red helmet Yellow/orange helmet
No injury 8 4 3 2
Injured or killed 20 2 1 1


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Conditions for using the chi-square test for independence:

  • Independence/Randomness Condition: The sample from our population should be independent, random sample or independent sample that can be considered representative of the population.
  • Large Sample Sizes Condition: The sample sizes need to be large enough so that the expected count in each cell is at least five.

  1. Wells, S., Mullin, B., Norton, R., Langley, J., Connor, J., Lay-Yee, R., & Jackson, R. (2004, April 10). Motorcycle rider conspicuity and crash related injury: case-control study. BMJ (Clinical research ed.), 328(7444), 857. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC387473/