what the question states :

"Events A and B are such that:

p(A) = 5/12

p(A|notB)=7/12

P(A intersection B ) =1/8 "

Would I be correct if I assume that Not B refers to A ? , so then i can draw a probability tree.

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- Dec 1st 2011, 08:00 AMterenceTwo events and a simple question
what the question states :

"Events A and B are such that:

p(A) = 5/12

p(A|notB)=7/12

P(A intersection B ) =1/8 "

Would I be correct if I assume that Not B refers to A ? , so then i can draw a probability tree. - Dec 1st 2011, 08:20 AMAmerRe: Two events and a simple question
- Dec 1st 2011, 08:20 AMcorsicaRe: Two events and a simple question
Most likely "notB" means "event B did

**not**occur"

I would also advise you to draw a Venn diagram for this question. - Dec 1st 2011, 09:01 AMPlatoRe: Two events and a simple question
- Dec 1st 2011, 09:55 AMterenceRe: Two events and a simple question
The question then asks for :

i) P(B)

ii) P(A|B)

iii) P(B|A)

iv) P(A U B)

P(B|A) is easy since P(A intersection B) / P(A) = 0.3

Had i known P(B) iv) would have been easy as well.

How can P(B) be found.. ?

Well I know this:

$\displaystyle \begin{align*}P(B) &= P(A\cap B) &+ P(notA\cap B)\end{align*}$

where

$\displaystyle \begin{align*}P(notA\cap B) &=P(A).P(B|notA)\end{align*}$ - Dec 1st 2011, 10:30 AMPlatoRe: Two events and a simple question
- Dec 1st 2011, 10:51 AMterenceRe: Two events and a simple questionQuote:

From the given you can find $\displaystyle P(A\cap B^C)$

the nearest i can get is that

$\displaystyle P(A\cap B^C) &= 7/12 * P(B)$ - Dec 1st 2011, 11:04 AMPlatoRe: Two events and a simple question
- Dec 1st 2011, 11:16 AMterenceRe: Two events and a simple question
Oh how dumb of me -.-

I should have reasoned that out. Largest problem with probability=> reasoning simple things out.

Thanks @Plato