Question

Suppose that P(A)=0.5, P(B)= 0.4 and P(B/A) =0.6. Find each of the following.

(a) P (A &B)
(b) P (A or B)
(c) P Are the events A and B independent. mutually exclusive, both, or neither?​

Answer 1

Part (a)

P(A) = 0.5

P(B) = 0.4

P(B/A) = 0.6

P(A and B) = P(A)*P(B/A)

P(A and B) = 0.5*0.6

P(A and B) = 0.3

Answer: 0.3

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Part (b)

We'll use the result from part (a)

P(A or B) = P(A) + P(B) - P(A and B)

P(A or B) = 0.5 + 0.4 - 0.3

P(A or B) = 0.6

Answer: 0.6

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Part (c)

A and B are not independent since P(B) does not equal P(B/A). The fact that event A happens changes the probability P(B). Recall that P(B/A) means "probability P(B) based on event A already happened". A and B are independent if P(B) = P(B/A).

Events A and B are not mutually exclusive since P(A or B) is not zero.

Answer: Neither