Create a 2 × 2 contingency table with the same totals in the margins as in Table 6.1. Assume you counted 16 concave malignant nuclei in Question 6. Fill in the rest of the table cells. Note that you can complete the other three table counts ( the concave benign, round malignant, and round benign) with just one known count value. Thus, only one table cell count is truly free— once one cell is determined, the other three are fixed. This demonstrates why 2 × 2 contingency tables have only 1 degree of freedom.