13. Estimate Model 2 (write out estimated model). Also, include the regression output below. (10 points) 14. Does completing homework improve performance on the final exam? Explain. (5 points) 15. Does missing classes in college affect performance on the final exam? Explain. (5 points) 16. What can you conclude about the effect of being a freshman based on the test? Explain. (10 points) 17. Do students with higher GPAs do better on the exam? Explain. (5 points) 18. Judging from all of the information on the description tab, what observations have been removed? Which of these removed observations were reasonable to remove, and which were