From the Guidelines
Fisher's exact test is the most appropriate statistical test for determining nonrandom associations between two categorical variables, particularly when sample sizes are small, as it calculates the exact probability rather than using approximations, giving precise p-values. This test is widely used in medical research, as seen in a study published in Circulation in 2019 1, where the 2-sided Fisher exact test was used to calculate the P-value for each outcome in a 2×2 contingency table. The key characteristics of Fisher's exact test include:
- It is used for categorical variables
- It is most appropriate when expected cell frequencies are less than 5
- It calculates the exact probability rather than using approximations
- It gives precise p-values that indicate whether the observed association is statistically significant
- The null hypothesis is that there is no association between the variables. To implement Fisher's test, one can use statistical software like R, SPSS, or online calculators where you input your contingency table data, as described by Walsh et al. and applied in the study published in Circulation 1. The test is particularly valuable in medical research, genetics, and other fields where sample sizes may be limited but precise statistical analysis is still required.
From the Research
Fisher Test Overview
- The Fisher test, also known as Fisher's exact test, is a statistical method used to determine if there are nonrandom associations between two categorical variables 2.
- It is commonly used in clinical settings to analyze the results of experiments and determine the significance of observed differences between groups 2, 3.
Applications of the Fisher Test
- The Fisher test has been used in various medical studies, such as evaluating the prognosis of patients with subarachnoid hemorrhage 4 and diagnosing auditory processing disorder 5.
- It has also been used in psychological research to analyze the results of experiments and determine the significance of observed differences between groups 3.
Limitations and Controversies
- The Fisher test has been criticized for being too conservative, resulting in greater resource requirements and more subjects exposed to an experimental treatment 2.
- There is an ongoing debate about the appropriate use of the Fisher test, with some researchers arguing that it should only be used in highly determined situations, while others argue that it can be used in exploratory science 3.