1. A surgeon wants to compare the number of successful skin grafts in a series o

Question

1. A surgeon wants to compare the number of successful skin grafts in a series of burn patients with the numbers published in other burn patients. A literature survey indicates that approximately 36.3% of burn patients with skin grafts become infected and that 77% of burn patients survive. The surgeon has had 15 patients out of 16 patients with skin grafts survive, with two infections. [2 pts each]

a) If we assume that our surgeon reflects what is in the literature survey (i.e. the probability of infection is 36.3%), what is the probability of the having only two infections out of 16 patients?

b) How many infections out of 16 would you have expected to see if the infection rate was 36.3%?

Explanation / Answer

a) P(2 infections out of 16) = 16C2 x 0.3632 x (1-0.363)14 = 0.0286

b) At a rate of 0.363, expected number of infections out of 16 = 0.363x16 = 5.808

So, we can expect 6 infections out of 16

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