63. The following data on HC and CO emissions for one particular vehicle was given in the chapter introduction.

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

a. Compute the sample standard deviations for the HC and CO observations. Does the widespread belief appear to be justi ed?

b. The sample coefficient of variation s/ (or 100 s/ ) assesses the extent of variability relative to the mean. Values of this coef cient 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.

x x #

x