In order to compare the mileage yields of 3 kinds of gasoline, several tests were run and the following results were obtained:

Gasoline A:

Gasoline B:

Gasoline C:

19 21 20 18 21 23 20 22 20 24 20 17 21 19 20

21 23 17

Carry out the analysis of variance test and test whether the observed differences between the means of 3 kinds of gasoline may be attributed to chance at 5% level of significance.