Use the DOS data to test whether there is gender and depression (dichotomized according to no and minor/major depression) association by stratifying medical burden and education levels, where medical burden has two levels (CIRS \(\leq 6\) and \(\operatorname{CIRS}>6\) ) and education has two levels (edu \(\leq 12\) and edu \(>12\) ). This is a problem of testing association for a set of four \(2 \times 2\) tables.