The article “Motor Vehicle Emissions Variability” (J. Air Waste Manag. Assoc. 1996: 667–675) reported the following hydrocarbon and carbon dioxide measurements using the Federal Testing Procedure for emissions-testing, applied four times each to the same car:

a. Compute the sample standard deviations for the HC and CO observations. Why should it not be surprising that the CO measurements have a larger standard deviation?
b. The sample coefficient of variation s/x̅ (or 100 · s/x̅) assesses the extent of variability relative to the mean. Values of this coefficient for several different data sets can be compared to determine which data sets exhibit more or less variation. Carry out such a comparison for the given data.

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HC (g/mile): CO (g/mile): 13.8 118 18.3 149 32.2 232 32.5 236