A study considered risk factors for HIV infection among intravenous drug users [11]. 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. 4.54 What is the probability that exactly 3 of 5 light users are HIV positive?

0.576

Step-by-step explanation:

For light users, given the Probability is X<100 is:

p = P(X < =100)= 40% = 0.4

q = 1 - 0.4 = 0.6

Given n=5 and x=3, we use Bernoulli probabilty distribution

P(X=x) = nCx ×(p)^x ×(q)^n-x

P(X=3) = 5C3 × (0.4)³ × (0.6)²

= 10 × 0.16 × 0.36

= 0.576

add all the numbers and check the ones place.

the answer is 486. as the ones place is more than 4, the estimation will be the next 10 ie, 490

answer: it's d

step-by-step explanation: