The following data give the starting salary for students who recently graduated from a local university and accepted jobs soon after graduation. The starting salary, grade-point average (GPA), and major (business or other) are provided.
(a) Using a computer, develop a regression model that could be used to predict starting salary based on GPA and major.
(b) Use this model to predict the starting salary for a business major with a GPA of 3.0.
(c) What does the model say about the starting salary for a business major compared to a nonbusiness major?
(d) Do you believe this model is useful in predicting the starting salary? Justify your answer, using information provided in the computer output.
Problem 4.20 (regression)
Bus and subway ridership in Washington, DC, during the summer months is believed to be heavily tied to the number of tourists visiting the city. During the past twelve years, the following data have been obtained.
(a) Plot the data and determine if a linear model is reasonable.
(b) Develop a regression model.
(c) What is the expected ridership if 10m people visit the city?
(d) If there are no tourists at all, explain the predicted ridership?
(e) Use excel to develop a regression model for the data in Problem 4.20. Explain what excel output indicates about the usefulness of this model.