The Centers for Disease Control and Prevention receives information about the causes for HIV/AIDS infection in the United States. Here are the causes of infection and their respective probability among American women age 20 to 24 years:
?
?
$\begin{array}{c}
\begin{array}{lll}
\bf{Cause}\
\text{Injection drug use} \
\text{Heterosexual sex} \
\text{Perinatal infection} \
\text{Other causes}
\end{array}
\begin{array}{lll}
\bf{Probability}\
? \
0.664 \
0.125 \
0.095
\end{array}
\end{array}$ This is a legitimate probability model. Therefore, what must be the probability that an American woman age 20 to 24 was infected via injection drug use?

Question

Quizplus · Accepted Answer

Since this is a legitimate probability model, the sum of all probabilities must equal 1. Therefore, the probability of infection via injection drug use must be:
1 - 0.664 - 0.125 - 0.095 = 0.116
So the answer is A, 0.116.

The Centers for Disease Control and Prevention Receives Information About