Select the options for missing values for Chi-Square Test for Association

Stat > Tables > Chi-Square Test for Association > Options

You can include missing data in the output table and calculations.

These options are only available when you have raw data. They are not available for summarized data.

Display for rows: Include a category in the table for missing values of the Row variable.
Display for columns: Include a category in the table for missing values of the Column variable.
Include displayed missing values in the calculations: Include displayed missing values in the calculations. By default, Minitab does not include missing values in the calculations.