# Thread: Simplify Var and Expected value?

1. ## Simplify Var and Expected value?

Suppose E(X) = 5 and Var(X) = 3.
FIND:
a) Var(2x+4)
___________MY ATTEMPT_____________

I used this formula from Wikipedia.
Var(ax+b) = Var(ax) = a^2Var(x)

Therefore,
2^2 Var(x) = 4*3 = 12
__________________________________

Someone told me the answer is 10, I dont know why.

Any tips

Thanks

2. ## Re: Simplify Var and Expected value?

Originally Posted by blackZ
Suppose E(X) = 5 and Var(X) = 3.
FIND:
a) Var(2x+4)
___________MY ATTEMPT_____________

I used this formula from Wikipedia.
Var(ax+b) = Var(ax) = a^2Var(x)

Therefore,
2^2 Var(x) = 4*3 = 12
__________________________________

Someone told me the answer is 10, I dont know why.

Any tips

Thanks
12 is right.

CB