Fretting is a wear process that results from

Chapter 1, Problem 64

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Fretting is a wear process that results from tangentialoscillatory movements of small amplitude in machineparts. The article Grease Effect on Fretting Wear ofMild Steel (Industrial Lubrication and Tribology,2008: 6778) included the following data on volumewear (1024mm3) for base oils having four differentviscosities.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 66.0 93.8 133.2 81.1252.6 30.6 24.2 16.6 38.9 28.7 23.6a. The sample coefficient of variation 100sy x assessesthe extent of variability relative to the mean (specifically,the standard deviation as a percentage of themean). Calculate the coefficient of variation for thesample at each viscosity. Then compare the resultsand comment.b. Construct a comparative boxplot of the data andcomment on interesting features.