The Case Study included information about the price for a full meal before and after the law change (in dollars). Of interest is whether the differences in price for a full meal before and after the law change (Price2 - Price1) differed, on average, between the four fast-food restaurant chains in New Jersey.
(a) Using PASW (SPSS) get the data directly from Cecil. In the window that appears select Save. Click OK and when prompted save the file to a relevant folder.
(i) The window that opens may be hidden behind your browser.
(ii) The data should open in PASW (SPSS).
(b) Using PASW (SPSS), draw the appropriate box plot(s) for this data set. (You should consider the design of this study to ensure the relevant plot(s) is drawn.) Comment on any features in the plot(s) in terms of the original story.
(c) Perform an F-test on these data. Refer to your Lecture Workbook, Section E, PASW (SPSS)
[Note: Ensure that you complete Step 1 through to Step 4.]
(d) State the assumptions of the F-test in terms of the original story.
(e) Calculate the ratio of the sample standard deviation of the most variable fast-food restaurant chain to the sample standard deviation of the least variable fast-food restaurant chain.
(f) Comment on the validity of the F-test by briefly discussing each assumption.
(g) Assume that an F-test is an appropriate test to use here. (Note: It may not be.)
(i) State the null hypothesis for the test, both in words and using symbols.
(ii) State the alternative hypothesis for the test in words.
(iii) What does the result of the F-test tell you about the mean difference in price for a full meal for the 4 fast-food restaurant chains? Explain your answer in 1 or 2 sentences.
(h) Assuming the Tukey's pairwise comparisons are valid:
(i) Is there a difference between the underlying mean difference in price for a full meal for Burger King fast-food restaurants in New Jersey and that for Wendy's fast-food restaurants in New Jersey? Interpret your results, including the 95% confidence interval.
(ii) Between which pair (or pairs) of chains were there significant differences (at the 5% level) in the mean difference in price for a full meal?
(iii) Are we able to determine which single chain has the greatest underlying mean difference in price for a full meal? If so, name the chain.