Math Is Fun Forum

juantheron

Member

Registered: 2011-10-19

Posts: 312

probability in interval

If A and B are two events such that

and

Then

(i)

(ii)

(iii)

(iv)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: probability in interval

Hi;

i) A intersection B is like A and B you can multiply A * B.

What is

The notation is incorrect. You mean?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

jonny

Guest

Re: probability in interval

Yes bobbym yor are saying right i mean P(A|B)

but cant understand for P(A intersection B) = P(A).P(B)

which is possible only when A and B are Independent events

and here we have to find range of   P(A intersection B)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: probability in interval

You could say:

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

jonny

Guest

Re: probability in interval

so how can i find range of P(A intersection B)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: probability in interval

Hi juan;

Sorry, I am not getting it. I will post if I think of something or maybe someone else will.

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

jonny

Guest

Re: probability in interval

answer given is P(A intersection B) = [4/15 , 3/5]

Let P(A intersection B) = x

I use the formula P(A U B) = P(A)+P(B)-x

Now 0<=P(A U B)<=1

then put  0<=P(A)+P(B)-x <=1

0<=19/15-x<=1

-1<=x-19/15 <=0

4/15 <= x <= 19/15

put right side is not match

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: probability in interval

hi

Now 0<=P(A U B)<=1

This is where you are going wrong.

The Union cannot be as low as zero.

The smallest Union is when all of A is contained in B, ie.  2/3

So you should have

2/3 <= P(A U B)<=1

Then your algebra will work.

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

jonny

Guest

Re: probability in interval

thank bobbundy got it

now how can i solve (ii) and (iii) and (iv)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,649

Re: probability in interval

hi jonny

You have done (ii) when you worked out (i)

For (iii) and (iv) you can use this from bobbym's post 4

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob