9.23 Healthy Eating Canadians are becoming more conscious about the importance of good nutrition, and some researchers believe we may be altering our diets to include less red meat and more fruits and vegetables. To test the theory that the consumption of red meat has decreased over the last 10 years, a researcher decides to select hospital nutrition records for 400 subjects surveyed 10 years ago and to compare their average amount of beef consumed per year to amounts con- sumed by an equal number of subjects interviewed this year. The data (in kg) are given in the table.  a. Do the data present sufficient evidence to indicate that per-capita beef consumption has decreased in the last 10 years? Test at the 1% level of significance.

b. Find a 99% lower confidence bound for the differ- ence in the average per-capita beef consumptions for the two groups. (This calculation was done as part of Exercise 8.82.) Does your confidence bound confirm your conclusions in part a? Explain. What additional information does the confidence bound give you?

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Ten Years Ago This Year Sample mean 33.1 28.6 Sample standard deviation 11.3 12.7