Please see ACF plot attached (Python). I would like to understand why the shaded region of my plot takes a curved shape?
My understanding so far is that the confidence band changes because the variance is estimated by Bartlett’s formula however:
I would like to understand this formula and why it’s used on a ACF?
Has this got to do anything with the moving average process?
How does Bartlett’s formula for variance affect the confidence band? What are its assumptions?