I am having a hard time understanding ACF and PACF. I estimated a GARCH(1,1) model and now I am checking its standardized residuals. This is what I get:

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I can not really understand why the lag 0 has p-value=1. Also, the Ljung-Box test on std residuals is OK.


1 Answer 1


These are not $p$-values, these are estimated autocorrelations $\hat\rho(h)$ for $h=0,1,\dots,10$. $\hat\rho(0)=\widehat{\text{Corr}}(X_t,X_{t-0})=1$, obviously, thus the value of $1$ at lag $0$. The Ljung-Box test looks at lags other than zero, and these look fairly OK, so no wonder the result is "OK", as you put it.


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