The chi-square test looks at the variables on the side and top axes of a table and tests whether they are independent. For example, it can be used to show whether or not variations in political opinions depend on the respondent's age.

The test compares the actual counts in each cell with the counts that would be expected in each cell if there were no relationship between the variables. The chi-square statistic provides a summary of the discrepancy between the actual and expected counts. The greater the dependence between the two variables, the larger the discrepancy will be, so a large chi-square statistic indicates dependence between the two variables.

The p value associated with the chi-square test can be distorted if any cells in the table have very low expected counts (below 5).