Let A and B be events from a

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Answered question

2022-05-13

Let A and B be events from a sample space S, with P[A] = 0.85 and P[B] = 0.8. Specify the range of possible values for P[A ∪ B] (for example: 0.3 ≤ P[A ∪ B] ≤ 0.9).

Answer & Explanation

Nick Camelot

Nick Camelot

Skilled2023-05-13Added 164 answers

To solve the problem, let's denote the probability of events A and B as P[A] and P[B], respectively. We are required to determine the range of possible values for the probability of the union of events A and B, denoted as P[A ∪ B].
The probability of the union of two events can be found using the inclusion-exclusion principle. It states that:
P[AB]=P[A]+P[B]P[AB]
In this case, we are not given the probability of the intersection of events A and B, i.e., P[A ∩ B]. Therefore, we need to determine the range of possible values for P[A ∪ B] based on the given probabilities.
To find the minimum possible value for P[A ∪ B], we can assume that events A and B are mutually exclusive, meaning that they have no elements in common (i.e., their intersection is empty). In this scenario, the probability of the union of mutually exclusive events is simply the sum of their individual probabilities:
P[AB]min=P[A]+P[B]
Substituting the given probabilities, we have:
P[AB]min=0.85+0.8
Calculating the sum, we get:
P[AB]min=1.65
Therefore, the minimum possible value for P[A ∪ B] is 1.65.
To find the maximum possible value for P[A ∪ B], we can assume that events A and B are completely overlapping, meaning that they are identical (i.e., their intersection is equal to both A and B). In this case, the probability of the union of identical events is equal to the probability of either A or B:
P[AB]max=max(P[A],P[B])
Substituting the given probabilities, we have:
P[AB]max=max(0.85,0.8)
Calculating the maximum value, we get:
P[AB]max=0.85
Therefore, the maximum possible value for P[A ∪ B] is 0.85.
In summary, the range of possible values for P[A ∪ B] is:
1.65P[AB]0.85

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