hw3sol - Solutions to Homework 3 Problem 3.9 a. The mean...

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Solutions to Homework 3 Problem 3.9 a. The mean number of minutes is x i n = 615 + 135 + ··· + 105 15 = 6330 15 = 422 minutes. b. To compute the median we first put the day in ascending order. 105 135 180 210 245 250 265 380 395 420 430 615 690 830 1180 We have 15 observations, so the middle observation is the 8th observation. The value is of this observation is 380 minutes, so this is the median. c. To compute the 85th percentile, we first compute the index i using p = 85 and n = 15. i = ± p 100 n = ± 85 100 × 15 = (0 . 85)(15) = 12 . 75 This is not an integer, so we round up to 13. The 13th observation (and the 85th percentile) is 690 minutes. d. Since the 85th percentile is 690 minutes, at least 85% of people in this sample used less than the average number of minutes for a plan. Problem 3.11 First for the city data we have ¯ x = 16 . 2 + 16 . 7 + ··· + 16 . 2 13 = 202 . 6 13 = 15 . 58 mpg To find the median we write data in ascending order. 13.2 14.4 15.2 15.3 15.3 15.3 15.9
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hw3sol - Solutions to Homework 3 Problem 3.9 a. The mean...

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