Question

Given that P(A) = 0.3 and P(B) = 0.9, and P(A and B) = 0.18, determine P(B|A).
0.30
0.60
0.15
0.20

Answer 1

Is P(A and B) \[P(A \cup B)?\]

Answer 2

yes

Answer 3

ok P(A) = 0.3 and P(B) = 0.9, and P(A and B) = 0.18
P(B\A)=P(B)-P(A intersection B)
P(AUB)=P(A)+P(B)-P(A intersection B)--->P(A intersection B)=0.06
P(B\A)=0.9-0.06=0.84

Answer 4

Get it?

Answer 5

I think P(A and B) is supposed to be P(A n B) instead...since that answer isn't one of the choices...

Answer 6

I look at it from a Venn diagram view...

P(B|A) is P(B given A)...so we know A has occurred.

Using the shown diagram, we see that B, given A is P(A n B)/P(A) since A is the new sample space. So,
\[P(B|A)=.18/.3 = .6\]

Answer 7

Ok then..sorry...Idk these words in english....
So if P(A and B) = 0.18 is the intersection we get --->
And P(B\A)=P(B)-P(A intersection B)=0.9-018=0.72

Answer 8

Still not one of the choices she gave.

Answer 9

K..these are the formulas I know..Idk....let me see again :)

Answer 10

The conditional probability formula is \[P(B|A)=P(B n A)/P(A)\]
It asks for, what is the porbability that B has occurred, *given* the fact that A has occurred. So we're looking at what portion of B overlaps A.

Answer 11

Idk...sorry

Answer 12

No problem. I'm 99.99% sure the answer is .6

Answer 13

I've always thought that these formulas are same as when we're dealing with sets ...idk though

Answer 14

P(A) = 0.3; P(B) = 0.9, P(A and B) = 0.18

determine P(B|A).

P(AnB) = P(A)*P(B) when they are mutally exclusive events

P(B|A) = P(AnB)/P(A) when they are not mutually exclusive

Answer 15

Right, becuase P(B|A) = 0 if B and A are mutually exclusive

Answer 16

since P(AnB) = .27 if they were exclusive; and it says they equal .18 we know that they aint :)

.18 18
--- = -- = 6/10 = .6
.3 30

Answer 17

Wait...P(AnB) = 0 when they are mutually exclusive, right? SInce there would be no overlap?

Answer 18

no; P(AnB) when they are mutually exclusive means that A doesnt affect B

Answer 19

Ok...you're right. THe formulas are still there, but the definitions went out the window years ago.

Answer 20

a.b
--- = b when a and b are seperate entities
a

Answer 21

I was thinking disjoint...