10.42 Canada's Food Basics An advertisement for Food Basics claims that Food Basics has had consistently lower prices than four other full-service supermarkets. As part of a survey conducted by an "independent market basket price-checking company," the average weekly total, based on the prices (in $) of approximately 95 items, is given for two different supermarket chains recorded during 4 consecutive weeks in a particular month.

a. Is there a significant difference in the average prices for these two different supermarket chains?

b. What is the approximate p-value for the test con- ducted in part a?

c. Construct a 99% confidence interval for the difference in the average prices for the two supermarket chains. Interpret this interval.

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Week Food Basics Zehrs 1 234 254.26 256.03 240.62 255.65 231.90 255.12 234.13 261.18