Question

With your typical convenience store customer, there is a 0.23 probability of buying gasoline. The probability of buying groceries is 0.76 and the conditional probability of buying groceries given that they buy gasoline is 0.85. a. Find the probability that a typical customer buys both gasoline and groceries. b. Find the probability that a typical customer buys gasoline or groceries. c. Find the conditional probability of buying gasoline given that the customer buys groceries. d. Find the conditional probability of buying groceries given that the customer did not buy gasoline. e. Are these two events (groceries, gasoline) mutually exclusive? f. Are these two events independent?

Answer 1

Answer:

a) P ( A & B ) = 0.1995

b) P (A U B ) = 0.7905

c) P (A/B) = 0.2625

d) P(B/A')  = 0.194805

e) NOT mutually exclusive

f) NOT Independent

Step-by-step explanation:

Declare Events:

- buying gasoline = Event A

- buying groceries = Event B

Given:

- P(A) = 0.23

- P(B) = 0.76

- P(B/A) = 0.85

Find:

- a. Find the probability that a typical customer buys both gasoline and groceries.

- b. Find the probability that a typical customer buys gasoline or groceries.

- c. Find the conditional probability of buying gasoline given that the customer buys groceries.

- d. Find the conditional probability of buying groceries given that the customer did not buy gasoline.

- e Are these two events (groceries, gasoline) mutually exclusive?

- f  Are these two events independent?

Solution:

- a) P ( A & B ) ?

                     P ( A & B ) = P(B/A) * P(A) = 0.85*0.23 = 0.1995

- b) P (A U B ) ?

                    P (A U B ) = P(A) + P(B) - P(A&B)

                    P (A U B ) = 0.23 + 0.76 - 0.1995

                    P (A U B ) = 0.7905

- c) P ( A / B )?

                    P ( A / B ) = P(A&B) / P(B)

                                    = 0.1995 / 0.76

                                    = 0.2625

- d) P( B / A') ?

                   P( B / A') = P ( B & A') / P(A')

                   P ( B & A' ) = 1 - P( A / B) = 1 - 0.85 = 0.15

                   P ( B / A' ) = 0.15 / (1 - 0.23)

                                    = 0.194805

- e) Are the mutually exclusive ?

        The condition for mutually exclusive events is as follows:

                    P ( A & B ) = 0 for mutually exclusive events.

        In our case P ( A & B ) = 0.1995 is not zero.

        Hence, NOT MUTUALLY EXCLUSIVE

- f) Are the two events independent?

         The condition for independent events is as follows:

                    P ( A & B ) = P (A) * P(B) for mutually exclusive events.

        In our case,

                        0.1995 = 0.23*0.76

                        0.1995 = 0.1748 (NOT EQUAL)

        Hence, NOT INDEPENDENT