# Expected Value and Variance

• May 9th 2010, 11:44 PM
blueturkey
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
• May 10th 2010, 01:19 AM
CaptainBlack
Quote:

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
• May 10th 2010, 02:43 AM
blueturkey

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.
• May 10th 2010, 04:24 AM
CaptainBlack
Quote:

Originally Posted by blueturkey