78 CHAPTER 2 Descriptive Statistics 45. Scores The mean scores for students in a statistics course (by major) are shown below. What is the mean score for the class? 9 engineering majors: 85 5 math majors: 90 13 business majors: 81 46. Grades A student receives the grades shown below, with an A worth 4 points, a B worth 3 points, a C worth 2 points, and a D worth 1 point. What is the student’s grade point average? A in 1 four-credit class C in 1 three-credit class B in 2 three-credit classes D in 1 two-credit class 47. Final Grade In Exercise 41, an error was made in grading your final exam. Instead of getting 93, you scored 85. What is your new weighted mean? 48. Grades In Exercise 46, one of the student’s B grades gets changed to an A. What is the student’s new grade point average? Finding the Mean of a Frequency Distribution In Exercises 49–52, approximate the mean of the frequency distribution. 49. Social Media The average daily amounts of time (in minutes) spent on Instagram Time Spent (in minutes) Frequency 0 –29 9 30 –59 23 60 –89 12 90 –119 6 50. Social Media The average daily amounts of time (in minutes) spent on Snapchat Time Spent (in minutes) Frequency 0 –19 8 20 –39 8 40 –59 15 60 –79 10 80 –99 7 51. Ages The ages (in years) of the residents of a small town in 2021 Age (in years) Frequency 0 – 9 78 10 –19 97 20 –29 54 30 –39 63 40 – 49 69 50 – 59 86 60 – 69 73 70 –79 53 80 – 89 43 90 –99 15 52. Populations The populations (in thousands) of the counties in Montana in 2019 (Source: U.S. Census Bureau) Population (in thousands) Frequency 0 –19 46 20 –39 3 40 –59 1 60 –79 1 80 –99 1 100 –119 3 120 –139 0 140 –159 1 Identifying the Shape of a Distribution In Exercises 53–56, construct a frequency distribution and a frequency histogram for the data set using the indicated number of classes. Describe the shape of the histogram as symmetric, uniform, negatively skewed, positively skewed, or none of these. 53. Hospital Beds Number of classes: 5 Data set: The number of beds in a sample of 20 hospitals 167 162 127 130 180 160 167 221 145 137 194 207 150 254 262 244 297 137 204 180
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