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# Fretting is a wear process that results from tangential

ISBN: 9780321629111 32

## Solution for problem 64E Chapter 1

Probability and Statistics for Engineers and the Scientists | 9th Edition

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Problem 64E

Fretting is a wear process that results from tangential oscillatory movements of small amplitude in machine parts. The article “Grease Effect on Fretting Wear (10-4 mm3)of Mild Steel” (?Industrial Lubrication and Tribology?, 2008: 67–78) included the following data on volume wear for base oils having four different viscosities. a?. ?The sample coefficient of variation100s?x ?assesses the extent of variability relative to the mean (specifically, the standard deviation as a percentage of the mean).Calculate the coefficient of variation for the sample at each viscosity. Then compare the results and comment. b?. ?Construct a comparative boxplot of the data and comment on interesting features.

Step-by-Step Solution:

Answer : Step 1 of 3 : Fretting is a wear process that results from tangential oscillatory movements of small amplitude in machine parts. The article “Grease Effect on Fretting Wear (10-4 mm3)of Mild Steel” , included the following data on volume wear for base oils having four different viscosities. Viscosity Wear 20.4 58.8 30.8 27.3 29.9 17.7 76.5 30.2 44.5 47.1 48.7 41.6 32.8 18.3 89.4 73.3 57.1 66 93.8 133.2 81.1 252.6 30.6 24.2 16.6 38.9 28.7 23.6 Step 2 of 3 : a) The claim is to find the coefficient of variation. For that we have to find mean and standard deviation of each viscosity The formula for coefficient of variance = (s/x)100 So first we have to find the mean and standard deviation of the wear for each viscosity. xi Where, mean = n and s = variance Viscosity x s cv 20.4 40.17 22.50 56.01 30.2 38.83 11.52 29.66 89.4 84.083 27.16 32.30 252.6 27.1 7.55 27.86 The sample coefficient of variation is similar for the three highest oil viscosity levels (29.66, 32.30, 27.86) but is much higher for the lowest viscosity (56.01). At low viscosity, it appears that there is much more variation in volume wear relative to the average or “typical” amount of wear.

Step 3 of 3

##### ISBN: 9780321629111

Since the solution to 64E from 1 chapter was answered, more than 430 students have viewed the full step-by-step answer. The answer to “Fretting is a wear process that results from tangential oscillatory movements of small amplitude in machine parts. The article “Grease Effect on Fretting Wear (10-4 mm3)of Mild Steel” (?Industrial Lubrication and Tribology?, 2008: 67–78) included the following data on volume wear for base oils having four different viscosities. a?. ?The sample coefficient of variation100s?x ?assesses the extent of variability relative to the mean (specifically, the standard deviation as a percentage of the mean).Calculate the coefficient of variation for the sample at each viscosity. Then compare the results and comment. b?. ?Construct a comparative boxplot of the data and comment on interesting features.” is broken down into a number of easy to follow steps, and 102 words. The full step-by-step solution to problem: 64E from chapter: 1 was answered by , our top Statistics solution expert on 05/06/17, 06:21PM. This full solution covers the following key subjects: wear, mean, sample, results, variation. This expansive textbook survival guide covers 18 chapters, and 1582 solutions. This textbook survival guide was created for the textbook: Probability and Statistics for Engineers and the Scientists, edition: 9. Probability and Statistics for Engineers and the Scientists was written by and is associated to the ISBN: 9780321629111.

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