請問懂簡易統計學的人

1)3
2)only if X is independent of Y

Thanks zzz~
第一題我也覺得是3
但是var(theta*Y)=theta-squared*var(Y)
所以覺得怪怪的, how did theta become squared...

any constant taken out of the braket has to be squared.
just memorize it. (if u don`t need to prove)

then var(3)=9?

No.
Define c=constant, x=variable
var(c)=c
var(cx)=c^2var(x)

thanks zzz, you seem to be so good at this.. thanks for the answers.. I got an assignment to hand in that`s related to statistics.. Maybe I can ask you more when I got stuck..:)

i major in Statistics ^^
i hope i gave you the right answers tho.

a final question please?
gamma-0 is the variance of a variable
gamma-1 is the covariance for two variables taht`s one period part (I think you know this, right?)
Can we convert the expected value of Y_t-1 and Y_t-2 which are one period apart to be in terms of gamma?

You can choose not to answer if you think it`s too troublesome.. thanks ^^

sorry, the expected value of (Y_t-1 and Y_t-2), not the expected values for the two respectively.

1.常數的變異數=0,所以本題=0
2. E(XY)要=E(X)*E(Y),其前題是 X 與 Y 之間要互相獨立,否則會有共變異係數的問題,
所以本題要先看X 與 Y 之間的關係為何
以上提供參考