Thank you for your reply!
All of question I have fully understood except for question 10-"Will acf and pacf for all MA,AR,ARIMA,ARMA never be 0?".
From CS2 CMP-CH13-page11,"The ACF of a purely indeterministic process satisfies acf_k ->0 as k ->infinity.","We do not expect two values of a (purely indeterministic) time series to be correlated if they are a long way apart.",so I think it said that acf_k and pacf_k of all process will be 0 for large k, or it is just "close to 0" not "equal to 0"?
Here I want to confirm whether this applies to all processes, because CS2 CMP-CH13-page11 seems to conflict with the solution 14.7-(iv).
Last edited: Aug 26, 2023