In City A, Researchers Investigated High School Students' Alcohol Use

In City A, researchers investigated high school students' alcohol use patterns after the police captain announced a new task force charged with curbing underage drinking. The researchers wanted to determine whether underage drinking actually decreased after this announcement, and realized that City B, a city that was quite similar to City A, had not made any such announcement. If the researchers were to use a comparison time-series design, what potential problems would they be avoiding by not using a simple time-series design. In other words, (a) what additional information does a comparison time-series design provide over a simple time series design? (b) Furthermore, provide two examples for the variables and data that would be included in a comparison time-series design, with one example comparing City A and City B, and the other example only using City A.