Question

Christine has always been weak in mathematics. Based on her performance prior to the final exam in Calculus, there is a 65% chance that she will fail the course if she does not have a tutor. With a tutor, her probability of failing decreases to 35%. There is only a 75% chance that she will find a tutor at such short notice. a. What is the probability that Christine fails the course? (Round your answer to 4 decimal places.)

Answer 1

0.49

Explanation:

We apply conditional probability to solve this question.

We have Events X and Events Y

P(X) = Probability Christine fails the course = ??? Unknown

P(Y) = Probability Christine finds a tutor

= 0.35

P(Y') = Probability Christine does not find a tutor = 1 - 0.35 = 0.75

P(X|Y) = Decrease in her probability of failing = 0.35

P(X|Y') = Probability that she will fail the course if she does not have a tutor

P(X) = P(X|Y) × P(Y) + P(X|Y') × P(Y')

P(X) = 0.35 × 0.75 + 0.65 × 0.35

P(X) = 0.2625 + 0.2275

P(X) = 0.49

The probability that Christine fails the course is 0.49