I am following a tutorial on time series analysis. The plots below are of percent changes of prices for S&P500 index. The tutorial says the following, which I disagree with or don't understand.
It's quite similar to white noise, isn't it? However, there appears to be some significant serial correlation in the ACF, and PACF plots around lags 1, 10, 15, 18 and 21.
I don't see significant serial correlation in the ACF and PACF at lags 1,10,15,18 and 21. Do you?
