102 CHAPTER 3 Describing, Exploring, and Comparing Data 26. Earthquakes Use the magnitudes (Richter scale) of the 600 earthquakes listed in Data Set 24 “Earthquakes” in Appendix B. In 1989, the San Francisco Bay Area was struck with an earthquake that measured 7.0 on the Richter scale. That earthquake occurred during the warmup period for the third game of the baseball World Series. Is the magnitude of that World Series earthquake an outlier when considered in the context of the sample data given in Data Set 24? Explain. 27. Body Temperatures Refer to Data Set 5 “Body Temperatures” in Appendix B and use the body temperatures for 12:00 AM on day 2. Do the results support or contradict the common belief that the mean body temperature is 98.6oF? 28. Births Use the birth weights (grams) of the 400 babies listed in Data Set 6 “Births” in Appendix B. Examine the list of birth weights to make an observation about those numbers. How does that observation affect the way that the results should be rounded? In Exercises 29–32, compute the mean of the data summarized in the frequency distribution. Also, compare the computed means to the actual means obtained by using the original list of data values, which are as follows: (Exercise 29) 31.4 minutes; (Exercise 30) 140.6 minutes; (Exercise 31) 55.2 years; (Exercise 32) 240.2 seconds. 29. Daily Commute Time in Los Angeles (minutes) Frequency 0–14 6 15–29 18 30–44 14 45–59 5 60–74 5 75–89 1 90–104 1 30. Avatar Flight of Passage Wait Times 10 AM (minutes) Frequency 70–89 4 90–109 7 110–129 6 130–149 6 150–169 18 170–189 5 190–209 1 210–229 3 31. Age of President at First Inauguration (years) Frequency 40–44 2 45–49 7 50–54 10 55–59 10 60–64 6 65–69 3 70–74 1 32. Duration of Old Faithful Eruptions (sec) Frequency 125–149 1 150–174 0 175–199 0 200–224 3 225–249 34 250–274 12 33. Weighted Mean A student of the author earned grades of A, C, B, A, and D. Those courses had these corresponding numbers of credit hours: 3, 3, 3, 4, and 1. The grading system assigns quality points to letter grades as follows: A = 4; B = 3; C = 2; D = 1; F = 0. Compute the grade-point average (GPA) and round the result with two decimal places. If the dean’s list requires a GPA of 3.00 or greater, did this student make the dean’s list? 34. Weighted Mean A student of the author earned grades of 63, 91, 88, 84, and 79 on her five regular statistics tests. She earned grades of 86 on the final exam and 90 on her class projects. Her combined homework grade was 70. The five regular tests count for 60% of the final grade, the final exam counts for 10%, the project counts for 15%, and homework counts for 15%. What is her weighted mean grade? What letter grade did she earn (A, B, C, D, or F)? Assume that a mean of 90 or above is an A, a mean of 80 to 89 is a B, and so on.
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