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
|
p-value
|
|
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.