So if P(A) = 0.8 and P(B) = 0.7 then max probability is 1.5 ? That doesnt seem right.

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OK, since you post the question, can you offer the Answer?

Well I'm unsure hence I posted ?

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Though I agree with the maximum, but I have with minimum value. i think we can choose 0.2 NOT 0.3, since we think that at least B occur. then it would be 0.2.

range: 0.2-0.5.

You're correct.

Thanks Peter.
+1 Kudos

0.44

explain it, thanks

Please give the source of the question.

It's from the actual GRE.

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Sorry, could you tell us if this is a quantity comparison question or a multiple answer choice question ??

In the latter, could you provide the 5 answer choices ?'

Thank you for your collaboration. And please, when you post a question, post it in a proper manner and use the tags.

This way, you give a lot of help to the other students and the community as a whole.

Thank you, once again.

Regards

Hi, the question is a multiple choice question. And since It showed up on my GRE , I can't recollect the answer choices correctly. Although I do remember that the answer choices were ranges and one of the choice was 0.5 >= P >= 0.2.

Sorry for incomplete answers.

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If P(A) = 0.8 and P(B) = 0.7, then Events A and B have to be independent for P(A and B) to be 0. Since they are not (which we assume when not given otherwise) there must be some intersection of these events.
So, if P(A) is 0.8 and P(B) is 0.7 then P(A and B)maximum would be 1, since it can't exceed 1.

Don't you mean dependent ?

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No, I mean independent.
If P(A) = 0.7, P(B) = 0.8 and P(A and B)=0 then they must be independent events, which is not the case in this question. If they had given P(A) = 0.7 and P(B) = 0.8 in the question, they would have given certain value for P(A and B) as well.

If P(A) = 0.7, P(B) = 0.8 and P(A and B)=0 then they must be independent events?

no, they are mutually exclusively events, which intersection would not be allowed.

Your concept is weak. For independent events, events are said not to affect each other, but they can both occur.

For example, the tail of a coin can occur with a dice rolling 6.

however, mutually exclusively events would not allow both events to occur, for example the tail and the face of a coin can not both occur.

Also the it is the maximum of (A or B) NOT (A and B) is 1. you should draw 2 circles which one stands for P(A) 0.8, the other stands for P(B) 0.7. Then the maximum of (A and B) is 0.7 when P(B) 0.7 is included in P(A) 0.8.

That maximum of P(A or B) NOT (A and B) was an overlook. Sorry for that.

I know that independent events can occur together and in that case P(A and B) would be P(A)*P(B). Appreciate for the example. However, I just meant that P(A or B) can't be equal to 1.5 because if two events having probabilities 0.7 and 0.8, it is not possible to have zero intersection.