Adult consumers at three fast-food hamburger chains at lunchtime in New York City were approached as they entered the restaurant and asked to provide their receipt when exiting. In all, 3857 people participated in the study. The sample mean number of calories consumed was 857 and the standard deviation was 677.
a) The sample standard deviation is quite large. What does this tell you about number of calories consumed in a hamburger-chain lunchtime fast-food purchase in New York City?
b) Given the values of the sample mean and standard deviation and the fact that the number of calories consumed can't be negative, explain why it is not reasonable to assume that the distribution of calories consumed is normal.
c) Carry out a hypothesis test to determine if the sample provides convincing evidence that the mean number of calories in a New York City hamburger chain lunchtime purchase is greater than the lunch recommendation of 750 calories.
d) Would it be reasonable to generalize the conclusion of the test in Part (c) to the lunchtime fast-food purchases of all Adult Americans? Explain why or why not.
e) Explain why it is better to use the customer receipt to determine what was ordered rather than just asking a customer leaving the restaurant what he or she purchased?
f. Do you think that asking a customer to provide his or her receipt before they ordered could have introduced a potential bias?