I would like to use the auto-correlation plots of my data for subsampling. For example, if you look at the photo attached, the data seems to no longer be correlated at lag#9. Since each lag is 28 minutes, this means I should be able to subsample every 4 hours and 12 minutes to get an independent data set. However, the plot shows that the data becomes correlated again at lag#22.
My question is: is it appropriate to subsample every 4 hours and 12 minutes? Or is it only appropriate to subsample according to the last correlated lag (eg. lag#146 = 2 days, 20 hours and 8 minutes)?