The following data represent the cost of an oil change (in dollars) in three different geographic regions

Question:

The following data represent the cost of an oil change (in dollars) in three different geographic regions for two types of service centers. A specialty chain is an oil change facility that specializes in oil changes, while a general service station provides a wide array of services in addition to oil changes.

Location Peoria Service Center Chicago Bolingbrook 19.95 23.99 24.99 Specialty chain 27.95 29.95 26.99 23.99 28.99 19.95

(a) The prices of oil changes are approximately normally distributed. Verify the requirement of equal population variances.
(b) Determine if there is significant interaction between location and service center type.
(c) If there is no significant interaction, determine whether there is significant difference in the means for the three locations. If there is no significant interaction, determine whether there is significant difference in the means for the two service center types.
(d) Draw an interaction plot of the data to support the results of parts (b) and (c).
(e) If there is significant difference in the means for the three locations, use Tukey's test to determine which pairwise means differ using a familywise error rate of a = 0.05. If there is significant difference in the means for the service center type, use Tukey's test to determine which pairwise means differ using a familywise error rate of a = 0.05.