The probability that a person owns a sports car given that they subscribe to automotive magazine is 40%. We also know that 3% of the adult population subscribes to automotive magazine. The probability of a person owning a sports car given that they don’t subscribe to automotive magazine is 30%. Use this information to compute the probability that a person subscribes to automotive magazine given that they own a sports car

0.0398
0.0389
0.0368
0.0396

The correct answer is $\boxed{\text{B. }0.0389}$.

The probability that a person subscribes to automotive magazine given that they own a sports car is denoted by $P(S|C)$. We can calculate this probability using Bayes’ theorem:

$$P(S|C) = \frac{P(C|S)P(S)}{P(C)}$$

We are given that $P(C|S) = 0.4$, $P(S) = 0.03$, and $P(C) = 0.03 + 0.3 = 0.33$. Substituting these values into Bayes’ theorem, we get:

$$P(S|C) = \frac{(0.4)(0.03)}{(0.33)} = 0.0389$$

Therefore, the probability that a person subscribes to automotive magazine given that they own a sports car is $\boxed{\text{B. }0.0389}$.

Here is a brief explanation of each option:

  • Option A: $0.0398$. This is the probability that a person owns a sports car given that they subscribe to automotive magazine. This is not the probability that a person subscribes to automotive magazine given that they own a sports car.
  • Option B: $0.0389$. This is the correct answer.
  • Option C: $0.0368$. This is the probability that a person does not own a sports car given that they subscribe to automotive magazine. This is not the probability that a person subscribes to automotive magazine given that they own a sports car.
  • Option D: $0.0396$. This is the probability that a person owns a sports car. This is not the probability that a person subscribes to automotive magazine given that they own a sports car.