A recent survey shows that the probability of a college student drinking alcohol is 0.6. Further, given that the student is over 21 years old, the probability of drinking alcohol is 0.8. It is also known that 30% of the college students are over 21 years old. The probability of drinking or being over 21 years old is ________.
A) 0.24.
B) 0.42.
C) 0.66.
D) 0.90.

Question

Quizplus · Accepted Answer

The probability of drinking or being over 21 is calculated using the formula P(A ∪ B) = P(A) + P(B) - P(A ∩ B). Here, P(A) = 0.6, P(B) = 0.3, and P(A|B) = 0.8. So, P(A ∩ B) = P(A|B) * P(B) = 0.8 * 0.3 = 0.24. Therefore, P(A ∪ B) = 0.6 + 0.3 - 0.24 = 0.66.

A Recent Survey Shows That the Probability of a College