The following table shows the data from a study to compute the causal effect of antiretroviral therapy A on death Y in subjects infected with HIV. Individuals were classified as treated (A = 1) if they received antiretroviral therapy, and as untreated (A = 0) otherwise. Death is coded as Y = 1. The variable L represents CD4 count (1: low; 0: high). Assume that this is a conditional randomized experiment given L.

L = 0 L = 1 Y=1 Y=0 Y=1 Y=0 A =1 20 30 108 252 A = 0 40 10 24 16