I am unsure about the following problems, I put what I think the answer is, would appreciate any help. Thanks!
1. For two events A and B, suppose P(A)= .45, P(B)=.75 and P(BlA)= .45
Are A and B independent?
I said no. For them to be independent, P(BlA) would have to equal .75
2. The events A and B are mutually exclusive. If P(A)= .4 and P(B)=.5 what is P(A and B)?
I feel like this might be a trick question? I thought mutually exclusive refered to P(A or B). If it means the same as independent then I answered
P(A and B)=P(A)*P(B)
3. Given P(A and B)= .25, P(A)= .20 and P(A and B)= .30 find P(B)
Just rearranging I got:
P(A or B)= P(A) + P(B) - P(A and B)
P(B) = P(A or B) - P(A) + P(A and B)
well you have three totaly different answers coming...
Originally Posted by kittysnyde
1. is correct ...
if you have indep then P(B|A)=P(B)
2. You're wrong here...
Indep and ME are almost opposites
HOWEVER, you asked for P(A and B)=P(AB)=0
ME means that the intersection is empty, hence the probability is zero.
3. Doesn't make sense
YOU seem to be mixing up and's (which are intersections) with or's (unions).