Fretting is a wear process that results from tangential oscillatory movements of small a...

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.