9.28 The file Fastfood contains the amount that a sample of nine customers spent for lunch (S) at a fast-food restaurant: 4.20 5.03 5.86 6.45 7.38 7.54 8.46 8.47 9.87 a. At the 0.05 level of significance, is there evidence that the mean amount spent for lunch is different from $6.50? b. Determine the p-value in (a) and interpret its meaning. c. What assumption must you make about the population distribution in order to conduct the test in (a) and (b)? d. Because the sample size is 9, do you need to be con- cerned about the shape of the population distribution when conducting the t test in (a)? Explain