Using the data for Problem 16.15 that represent the number of new, single-family houses sold in the United States from 1992 through 2018 (stored in House Sales),
a. Fit a third-order autoregressive model to the new single-family homes sold and test for the significance of the third-order autoregressive parameter. (Use a = 0.05 .)
b. If necessary, fit a second-order autoregressive model to the new single-family homes sold and test for the significance of the second-order autoregressive parameter. (Use a = 0.05.)
c. If necessary, fit a first-order autoregressive model to the new single-family homes sold and test for the significance of the first-order autoregressive parameter. (Use a = 0.05.)
d. If appropriate, forecast the new single-family homes sold in 2019.

Problem 16.15

The file House Sales contains the number of new, single-family houses sold in the United States from 1992 through 2018.
a. Plot the data.
b. Compute a linear trend forecasting equation and plot the trend line.
c. Compute a quadratic trend forecasting equation and plot the results.
d. Compute an exponential trend forecasting equation and plot the results.
e. Which model is the most appropriate?
f. Using the most appropriate model, forecast the number of new, single-family houses sold in the United States in 2019.