12.30 The Bell Telephone Company’s long-distance phone charges may appear to be exorbitant when compared with the charges of some of its competitors, but this is because a comparison of charges between competing companies is often analogous to comparing apples and eggs. Bell’s charges for individuals are on a per-call basis. In contrast, its competitors often charge a monthly minimum long-distance fee, reduce the charges as the usage rises, or do both. Shown in Table 12.11 is a sample of long-distance charges from Orlando, Florida, to 12 cities for three non-Bell companies offering long-distance service. The data were reported in an advertisement in the Orlando Sentinel, March 19, 1984.
A note in fine print below the advertisement states that the rates are based on “30 hours of usage” for each of the servicing companies.
The data in Table 12.11 are pertinent for companies making phone calls to large cities. Therefore, assume that the cities receiving the calls were randomly selected from among all large cities in the United States.
a What type of design was used for the data collection?
b Perform an analysis of variance for the data.
Present the results in an ANOVA table.
c Do the data provide sufficient evidence to indicate differences in mean charges among the three companies? Test by using  0.05.
d Company 3 placed the advertisement, so it might be more relevant to compare the charges for companies 1 and 2. Do the data provide sufficient evidence to indicate a difference in mean charges for these two companies? Test by using  0.05.