Suppose we wish to compare the probabilities of dying of a hospital-acquired infection between two hospitals. The following table summarizes the times (in days) of death or discharge for 200 subjects who acquired an infection in hospital A (denoted with subscript 1), and for 200 subjects who acquired an infection in hospital B (denoted with subscript 2). Use this table to answer the following questions. t R1 R2 R D1 D2 D C1 C2 C 0 200 200 400 0 0 0 0 0 0 2 200 200 400 7 15 22 8 1 9 4 185 184 369 18 21 39 2 8 10 6 165 155 320 20 38 58 2 6 8 8 143 111 254 30 25 55 31 38 69 10 82 48 130 18 15 33 43 28 71 t = time (in days) R = number at risk at the start of that time point D = number of deaths in that time point C = number censored in that time point.

Using the log-rank test, compare the survival curves for dying of a hospital-acquired infection between two hospitals.

Let S₁(t) be the true population cumulative survival for dying of a hospital-acquired infection in Hospital A and S₂(t) the true population cumulative survival for dying of a hospital-acquired infection in Hospital B

H₀: S₁(t) = S₂(t)

H₁: S₁(t) S₂(t)

What is the continuity-corrected ²statistic? (round answer to at least 2 decimal places)