Chapter 1 Question 7 - Page 35:

Let A and B be events such that P(A∩B) = 1/4, P( ˜ A) = 1/3, and P(B) = 1/2. What is P(A∪B)

Answer

If events are independent

\[P(A \cap B) = P(A)*P(B)\]

\[P(A \cap B) = 1/4\]

\[P(\overline{A})=1/3\]

probability_a_complement=1/3

probability_a= 1- probability_a_complement

probability_b= 1/2

probability_a_and_b = probability_a * probability_b

probability_a_and_b
## [1] 0.3333333

\[P(A \cap B) \neq P(A)*P(B)\]

Based on this, the events are not mutualy exclusive and dependent. In this case:

\[P(A \cup B) = P(A)+P(B)-P(A \cap B)\]

probability_a_or_b = probability_a + probability_b - probability_a_and_b
probability_a_or_b
## [1] 0.8333333

The answer is 0.83