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Review of Probability

Probability of Not Mutually exclusive events:

When two events are not mutually exclusive, that is they can happen at the same time, we use this formula:

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

For example:


If P(A)=0.60 and P(B)=0.30 are independent and not mutually exclusive,then find P(A or B)


1) Find P(A and B ) first


P( A and B) = (0.6)(0.30) = 0.18


2) Now apply the formula


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

P(A or B) = 0.60 + 0.30 - 0.18 = 0.72