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onethemie he Transplant operations have become routine. One common transplant op

ID: 3043508 • Letter: O

Question

onethemie he Transplant operations have become routine. One common transplant operation is for kidneys. The most dangerous aspect of the procedure is the possibility that the body may reject the new organ. There are several new drugs available for such circumstances and the earlier the drug is administered, the higher the probability of averting rejection. The New England Journal of Medicine recently reported the development of a new urine test to detect early warning signs that the body is rejecting a transplanted kidney. However, like most other tests, the new test is not perfect n act, 20% of negative tests and 10% of positive tests prove to e incorrect. Physiciars know h in about 31% ki ne transplant he bo tres o reect he or an e new test has a positive resul (indicating early warning of rejection), what is the probability that the body is attempting to reject the kidney? amed adne bto reject the on Probability =

Explanation / Answer

probability of positive test =P(body rejecting and test positive+body not rejecting and test positive)

=0.31*(1-0.20)+(1-0.31)*0.1=0.317

therefore probability of body rejecting the kidney given positive test

=P(body rejecting and test positive)/P(test positive) =0.31*(1-0.20)/0.317 =0.782334