Two-by-two contingency table

	Event
Group	Occurred (Y=1)	Not occurred (Y=0)	Total
Treatment (X=1)	n_11,1+n_10,1	n_00,1+n_01,1	n_11,1+n_10,1+n_01,1+n_00,1
Control (X=0)	n_11,0+n_01,0	n_00,0+n_10,0	n_11,0+n_10,0+n_01,0+n_00,0
Total	n₁₁+n_10,1+n_01,0	n₀₀+n_01,1+n_10,0	n

Table 3: Two-by-two contingency table with the numbers for the four types of subjects defining the four principal strata.