Hi all, Had a question I wanted to clarify as follows:- If Y_t =at + sum (i=1 to t) e_i Then why would Y_(t-s) =as + sum (i=1 to t-s) e_i I'm not sure why the term is "as" instead of "a(t-s)" Thanks!
Hi Laura I think I agree with with you here as you've written it. Where are you seeing this in the course? Thanks Andy
Hi Andy, It's from Q6ii CT6 2010 Apr in the expansion of the cov(y_t, y_(t-s)). I'm not sure why the term is "as" instead of "a(t-s)" in this case. Thanks!
Hi Laura Appears to be a typo in the Examiners' report here. What you had is correct. The final answer is still \( (t-s) \sigma^2 \) Hope this helps! Andy
