quiz2Sp2011_key

quiz2Sp2011_key - Answer: IQR = Q 3-Q 1 = 2 . 4-. 7 = 1 . 7...

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NAME: Stat 205 Quiz 2 The following are the same n = 20 times in minutes to complete a task (involving stacking blocks given to preschoolers) that you analyzed on Quiz 1. Here they are ordered. The sample mean is ¯ y = 1 . 875 and the sample standard deviation is s = 1 . 181 . 0.1 0.2 0.3 0.6 0.7 0.7 0.8 0.8 0.9 1.1 1.4 1.4 1.8 2.1 2.1 2.7 3.3 4.1 5.7 6.7 1. Find the five number summary of these data: y (1) , Q 1 , Q 2 , Q 3 , and y (20) . Answer: y (1) = 0 . 1 , Q 1 = 0 . 7 + 0 . 7 2 = 0 . 7 , Q 2 = 1 . 1 + 1 . 4 2 = 1 . 25 , Q 3 = 2 . 1 + 2 . 7 2 = 2 . 4 , y (20) = 6 . 7 . 2. What percentage of the data points are larger than than Q 3 ? Answer: 5 20 = 0 . 25 = 25% . 3. Make a regular boxplot from the 5 number summary. 4. Find the interquartile range IQR . Is it larger than the standard deviation?
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Unformatted text preview: Answer: IQR = Q 3-Q 1 = 2 . 4-. 7 = 1 . 7 . Yes, 1 . 7 = IQR > s = 1 . 181 . 5. Find the lower and upper fences. Which, if any, observations are outliers? Answer: LF = Q 1-1 . 5 IQR = 0 . 7-1 . 5(1 . 7) =-1 . 85 , UF = Q 3 + 1 . 5 IQR = 2 . 4 + 1 . 5(1 . 7) = 4 . 95 . There are two outliers: 5.7 and 6.7 minutes. 6. Compare the mean to the median. Is the mean pulled in the direction of skew? Comment. Answer: The mean y = 1 . 875 is larger than the median Q 2 = 1 . 25 . The data are skewed right, so yes the mean is pulled in the direction of skew....
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