# Homework Help: Find mean and variance of X and Y

1. Sep 11, 2010

### phillyolly

1. The problem statement, all variables and given/known data

I have found the marginal distribution for X and Y from a table. (No statistical regression, just simple table)
How should I proceed in finding mean, variance an correlation coefficient of X and y? I am computing by hand.
Thank you,

2. Relevant equations

3. The attempt at a solution

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2. Sep 11, 2010

### phillyolly

Is mean for X:

(1/8+3/8+3/8+1/8)
-------------------
4

and mean for Y is

(2/8+4/8+2/8)
--------------
3

?

3. Sep 11, 2010

### vela

Staff Emeritus
No. Remember the mean of a random variable is defined as

$$\bar{X} = \sum_i x_i P_X(x_i)$$

It's the sum of the product of the values X can take on multiplied by probability of that value.