A movie company wishes to measure the effect of advertising on box of?ce receipts. Thirty U.S. cities with similar demographics are chosen for an experiment. The thirty citiesare randomly divided into three groups of ten cities. In each city a trailer for a new ?lm will be run on a local cable station during prime time in the week leading up to the release of the ?lm. In the ?rst group of ten cities the trailer will be run 500 times, in the second group the trailer will be run1,000 times, and in the third group it will be run 1,500 times.The company will collect the box of?ce receipts for the opening weekend of the ?lm in each city and compare the mean box of?ce receipts.

Explain why this is a designed experiment.
Identify the factor and the response variable.
Is the factor quantitative or qualitative?
Identify the factor levels and the experimental units.
What part of choosing the cities is not necessarily random?
Explain why it might be dif?cult to randomize this part of the experiment.