a. Calculate and display the first 50 autocorrelations for the four data series in the table for this exercise, labeled A, B, C, and D; consider each of the four data series to be a quarterly time series. How many of the autocorrelations fall outside the 95 percent confidence interval (positive or negative)?

b. Is there a pattern to those autocorrelation coefficients falling outside the 95 percent confidence interval?

c. Calculate and display the first 50 partial autocorrelations for the 100 time-series observations. How many of the partial autocorrelation coefficients fall outside the 95 percent confidence interval?

d. Is there a pattern to those partial autocorrelation coefficients falling outside the 95 percent confidence interval?

e. Which frame in Figures 7.1, 7.3, and 7.5 does this pattern of autocorrelation and partial autocorrelation coefficients most closely resemble?

f. Estimate the appropriate model as determined from your inspections carried out in parts a through e, and forecast for four quarters into the future. Calculate the RMSE for each model.

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