# Find the Mean and Variance of Random Variable Z = (5x+3)

1. Mar 2, 2012

### rogo0034

1. The problem statement, all variables and given/known data
Find the Mean and Variance of Random Variable Z = (5x+3)

Using data set:

Using:

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3. The attempt at a solution

Last edited: Mar 2, 2012
2. Mar 2, 2012

### rogo0034

Sorry the data set it so large, i've been trying to adjust it to no avail.

EDIT: Fixed it, should be easier to view now

Last edited: Mar 2, 2012
3. Mar 2, 2012

### Ray Vickson

You have a very small table of x and f(x) values. What is stopping you from computing EX? Why don't you just compute EX, then use that value in the computation of Var(X) = sum f(x)*(x-EX)^2 ?

RGV

4. Mar 3, 2012

### rogo0034

They want us to use the theorem and corollary, any ideas? i'm not too savvy with this stuff yet.

5. Mar 3, 2012

### Ray Vickson

OK, so use the theorem and the corollary. Does the first theorem have E(X) in it? Do you know the value of E(X)? If not, you need to compute it. Does the second theorem have $\text{Var}(X) = \sigma_x^2$ in it? Do you know the value of Var(X)? If not, you need to compute it.

RGV