The Chi-Square statistic is a mathematical equation often used to test the relationship between two or more categorical variables. The test’s null hypothesis is that no relationship between two or more variables can exist; they are entirely independent. By comparing the pattern of responses that can be observed to the anticipated pattern of truly independent categorical variables, researchers can compare a critical value from the Chi-Square distribution to the calculated Chi-Square statistic to determine if an association does, in fact, exist. It’s important to be aware that the Chi-Square statistic is quite sensitive to sample size; in larger sample sizes, small differences will appear more statistically significant than they are. Researchers can mitigate this issue by choosing appropriately sized samples and merging categories when possible to create a smaller table. Dental health professionals often use the Chi-Square statistic to determine causal relationships between types of treatment and patient outcomes.