44. Progress rate. Grade Point Average (GPA) and Progress Rate (PR) are two variables of crucial importance to stu- dents and schools. While each class's GPA data is typically bell shaped, the PR data is quite different. Here is a histo- gram and summary statistics from a large class of business students in a European university, where PR is determined as the share of the 60 yearly European Credit Transfer and Accumulation System (ECTS) points achieved by any student. -5 0 5 10 15 20 25 30 35 40 45 50 55 60 Mean 40.596317 100.0% maximum 60 Std Dev 22.290204 99.5% 60 Std Err Mean 0.6849613 97.5% 60 Upper 95% Mean 41.940354 90.0% 60 Lower 95% Mean 39.25228 75.0% quartile 60 N 1059 50.0% median 53.5 25.0% quartile 17 10.0% 6.5 2.5% 0 0.5% 0.0% minimuma) Which is a better summary of the typical PR, the mean or the median? Explain. b) Which is a better summary of the spread, the IQR or the standard deviation? Explain. c) From a Normal model, about what percentage of stu- dents are within one standard deviation of the mean PR? d) What percentage of students actually are within one standard deviation of the mean? e) Explain the problem in using the Normal model for these data