Final answer:
The design of this study is an observational study that compared the sales of Coca-Cola Classic, New Coke, and Pepsi in public building vending machines using a random sample of 10 buildings in Chicago.
Step-by-step explanation:
The design of this study is an observational study. The researchers randomly selected 10 public buildings in Chicago that had both a Coke machine, selling Coca-Cola Classic and New Coke, and a Pepsi machine. They recorded the number of cans sold over a given period of time. The purpose of the study was to compare the sales of Coca-Cola Classic, New Coke, and Pepsi in these public building vending machines.