Posted by David on Tuesday, February 24, 2009 at 2:56pm.
Two independent events, A and B, satisfy Pr(A) = 0.6 and Pr(B) = 0.3. In the case of Pr(A or B), why isn't the answer 0.3? We are looking at the probability of A or B. I choose B.
Thank you!

Probability/Statistics  drwls, Tuesday, February 24, 2009 at 4:02pm
The answer is Prob(A) + Prob(B)  Prob (A + B)= 0.6 + 0.3  0.18 = 0.72
The last term avoids double counting of the occurence of both A and B, which satisfied the "A or B" criterion only once.
The answer is certainly not 0.3, since 60% of the events are A and satisfy the A or B requirement
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