Table 1.

Observed frequencies in two screening studies

	Disease Status (d = 1)				Disease Status (d = 2)				Disease Status (d = 3)				Total n
	$x_{11}^1$	$x_{10}^1$	$x_{01}^1$	$x_{00}^1$	$x_{11}^2$	$x_{10}^2$	$x_{01}^2$	$x_{00}^1$	$x_{11}^3$	$x_{10}^3$	$x_{01}^3$	$x_{00}^3$
Study 1	13	144	95	?	10	24	21	?	—	—	—	—	20,221
Study 2	11	20	81	?	6	29	48	?	14	15	4	?	5,192

Note: Study 1, Health Insurance Plan Screening Study for Breast Cancer in New York. Study 2, a multicenter study for screening cervical cancer.