ACF/PACF plots of both the sample and the r
I can’t upload the text but I can say that the time series of interest is the NASDAQ composite index which Figure 1 shows the raw (IXIC) and the first differenced (dIXIC) data together with the estimated autocorrelation and partial autocorrelation functions. An ARIMA(2,1,1) model has been fitted.
My problems are: which model can I suggest that can improve the results?
What are the information that can give me the ACF plot of the residuals? What about the standardized residuals, the p-values and the squared residuals? (FIGURE 2 and 3)
Basically, what is the difference from consulting the ACF plot of the sample data vs. the ACF of the residuals? Do they give different information?
* Attachment 1
* Attachment 2
* Attachment 3