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August 9th, 2011, 01:48 AM   #1
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Probability

P(A)=0.30 P(B)=0.45 P(A?B)=0.75
P(A?B)=P(A?B)/(P(B))=0.75/0.45=1.667
P(B?A)=P(A?B)/(P(A))=0.75/0.30=2.5
P(A?B)=P(A)+P(B)-P(A?B)=0.30+0.45-0.75=0

P(A)=0.30 P(B)=0.45 and A and B are independent
P(A?B)=P(A)=0.30
P(B?A)=P(B)=0.45
P(A?B)=P(A)P(B)=0.300.45=0.135
P(A?B)=P(A)+P(B)-P(A?B)=0.30+0.45-0.75=0

P(A)=0.30 P(B)=0.45 and A and B are mutually exclusive
P(A?B)=0
P(B?A)=0
P(A?B)=0
P(A?B)=P(A)+P(B)-P(A?B)=0.30+0.45-0=0.75

Can anyone confirm that all my answer are correct? I was having some difficulty but i've attempted all the questions to show that i've had a go.
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August 9th, 2011, 01:17 PM   #2
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Re: Probability

The first one is absolutely incorrect. P(A)=0.30 P(B)=0.45 P(A?B)=0.75 - can't be. The probability of an intersection is at most the probability of the smaller.

The second has an error at the end. P(A?B)=P(A)+P(B)-P(A?B)=0.30+0.45-0.75=0 - you used the wrong value for the probability of intersection. The line before you had it 0.135 (correct value).


The third is correct.
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