SOLUTION: sorry if am adding more questions but please i need your help. The next question is a. A study considered risk factors for HIV infection among intravenous drug users. It found t

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Question 483266: sorry if am adding more questions but please i need your help.
The next question is
a. A study considered risk factors for HIV infection among intravenous drug users. It found that 40% of users who had 100 injections per month (light users) and 55% of users who had >100 injections per month (heavy users) were HIV positive.
i. What is the probability that exactly 3 out of 5 light users are HIV positive?
ii. What is the probability that at least 3 light users are HIV positive?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
a. A study considered risk factors for HIV infection among intravenous drug users.
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It found that 40% of users who had 100 injections per month (light users) and
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55% of users who had >100 injections per month (heavy users) were HIV positive.
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i. What is the probability that exactly 3 out of 5 light users are HIV positive?
Binomial Problem with n = 5 and p = 0.40
P(x = 3) = 5C3(0.4)^3*(0.6)^2 = 0.2304
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ii. What is the probability that at least 3 light users are HIV positive?
P(3<= x <=5) = 1 - binomcdf(5,0.4,2) = 0.3174
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Cheers,
Stan H.
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