About 10 years ago Washington DC was considering a new law to help combat obesity. The law would require that chain restaurants post calorie counts for all items on their menus. Before the bill's adoption, researchers wanted to determine whether the law would be effective. For over a year, researchers gathered data on every transaction at Dunkin' Donuts shops in Washington DC and determined that the population mean calories purchased by customers at stores without calorie postings was 250 calories. After calories were posted, a sample of 71 transactions at Dunkin' Donuts shops had a mean of 234 calories and a standard deviation of 166 calories. (a) What is the population that the researchers are studying?

a. All customers at Dunkin' Donuts shops in Washington DC

b. All Dunkin' Donuts shops in Washington DC

c. All calorie counts of purchases at Dunkin' Donuts shops in Washington DC

d. All transactions at Dunkin' Donuts shops in Washington DC

(b) What is the response variable that the researchers are interested in?

a. Change in calories purchased

b. Average calories per purchase

c. Difference in calories purchased

d. Number of calories purchased

(c) What is the explanatory variable?

a. Whether calories were posted or not

b. The location of the shop

c. Number of calories purchased

d. The year that data was collected

(d) What kind of study is this?

a. Observational study

b. Experiment

c. Survey

d. Census

(e) What are appropriate hypotheses to answer the research question being studied?

a. H₀: = 250

and

H_a: < 250

b. H₀: < 250

and

H_a: = 250

c. H₀: < 234

and

H_a: = 234

d. H₀: = 234

and

H_a: < 234

(f) If researchers concluded that calorie counts were significantly lower when they were posted, can they conclude that it was caused by the calorie posting?

a. No, because it was an experiment, not an observational study.

b. Yes, because it was an observational study, not an experiment.

c. No, because it was an observational study, not an experiment.

d. Yes, because it was an experiment, not an observational study.