Comparing means of three or more groups.
There are 4 auto body shops in a community and all claim to promptly serve customers. To check if there is any difference in service, customers are at random selected from each repair shop and their waiting times in days are recorded. The output from a statistical software package is:
Summary

Groups

Count

Sum

Average

Variance

Body Shop A

3

15.4

5.133333

0.323333

Body Shop B

4

32

8

1.433333

Body Shop C

5

25.2

5.04

0.748

Body Shop D

4

25.9

6.475

0.595833

ANOVA

Source of Variation

SS

df

MS

F

pvalue

Between Groups

23.37321

3

7.791069

9.612506

0.001632

Within Groups

9.726167

12

0.810514



Total

33.09938

15




Is there proof to suggest a difference in the mean waiting times at the four body shops? Use the .05 significance level.