A Test Was Conducted to Compare the Miles Per Gallon $24,22,23,25,22,21$

Essay

A test was conducted to compare the miles per gallon obtained by three sub-compact automobiles. The following data (in miles per gallon) were obtained from 6 full tanks of the same gasoline.
I. $24,22,23,25,22,21$
II. $23,22,26,24,27,25$
III. $30,28,26,27,26,24$
Use a nonparametric test to evaluate whether or not there are significant differences in gasoline economy among the automobiles. Use $\alpha=0.05$ .