# Thread: Expected Value and Variance

1. ## Expected Value and Variance

I'm having a bit of trouble just starting a question, which I've attached.

The answer is E(yt) = 0 but how do you go about working that from the information given?

Any tips to point me in the right direction?

Thanks for the help

2. Originally Posted by blueturkey
I'm having a bit of trouble just starting a question, which I've attached.

The answer is E(yt) = 0 but how do you go about working that from the information given?

Any tips to point me in the right direction?

Thanks for the help
$y_t$ is the sum of three zero mean RV's (thay are independednt but that does not matter for the mean) and so its expectation is zero.

CB

Does this mean that I should assume,

E(et) = E(et-1) = E(et-2) = 0

but what is the basis of assuming this?

Alternatively, I'm guessing that this may have something to do with the statement E(etet+tau) = 0, although I'm not sure what this statement means either.

4. Originally Posted by blueturkey