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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This note was uploaded on 01/24/2011 for the course STATISTICS 19897 taught by Professor Jager,abigaill during the Spring '10 term at Kansas State University.

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

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