Compare models Run the model to predict com yield using year

Compare models. Run the model to predict com yield using year and the squared term year2 defined in the previous exercise. Summarize the significance test results. The coefficient for year2 is not statistically significant in this run, but it was significant in the model analyzed in the previous exercise. Explain how this can happen. Obtain the fitted values for each year in the data set and use these to sketch the curve on a plot of the data. Plot the least-squares line on this graph for comparison. Do you see much of a difference between these two regression functions? Compute the difference between the two predicted values for each year and plot them versus year. For what years are the differences the largest? Do a prediction. Use the simple linear regression model with com yield as the response variable and year as the explanatory variable to predict the com yield for the year 2008, and give the 95% prediction interval. Also, use the multiple regression model where year and year2 are both explanatory variables to find another predicted value with the 95% interval.

Solution

The data is not available to perform the analysis