# Thread: How to find probability distribution and conditional probability distribution ?

1. ## How to find probability distribution and conditional probability distribution ?

I know one must use notation like

$P(x=1|U=4)=?$

$P(x=2|U=4)=?$

$P(x=3|U=4)=?$

How does one use these notations to derive the final answer for number two?

2. ## Re: How to find probability distribution and conditional probability distribution ?

Hey littlejon.

You have to group the values into "bins" and then find their frequencies.

After you do this, you make something a probability distribution by dividing each of the frequencies (for each bin) by the total number of all frequencies [i.e. the sum of frequencies].

3. ## Re: How to find probability distribution and conditional probability distribution ?

Do you see that there are only 6 possible outcomes for (x, y): (1, 1), (1, 2), (2, 1), (2, 2), (3, 1), and (3, 2)?
What are the probabilities for each of those?

And there are four possible outcomes for X+ Y: 2, 3, 4, and 5. 1+ 1= 2; 1+ 2= 2+ 1= 3; 2+ 2= 3+ 1= 4, and 3+ 2= 5. What are the probabilities of each of those?

If U= 4, then (x, y)= (2, 2) or (3, 1). So x has two possible outcomes, 2 or 3. What are the probabilities of x= 2 or 3 given that (x, y)= (2, 2) or (3, 1).