Part C Needle Injections The exposurecontraction rates for H

Part C Needle Injections The exposure/contraction rates for HIV through injection drug use has been estimated at 1.8% per exposure to an infected needle. 9. (1 mark) What is the probability a person using an infected needle does not contract H (consider only 1 exposure)? 10. (2 marks) Despite the risk, some share needles after some effort to clean them. Suppose that cleaning the needle after it carries HIV reduces the transmission rate to 0.8% per exposure to infected needle. Using this new transmission rate, what is the probability that a person uses 52 different infected needles (i.e. 52 different exposures and never contracts HIV in any of these 52 exposures? Assume that each exposure is independent of all others

Solution

9.

P(not infect) = 1 - 0.018 = 0.982 [ANSWER]

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10.

P(not infect after 52 needles) = (1-0.008)^52 = 0.658577595 [ANSWER]