Question: In each of the following examples, explain whether the experiment was doubleblind, single-blind, or neither, and explain whether it was a matched-pair or block design or neither.

a. A utility company was interested in knowing if agricultural customers would use less electricity during peak hours if their rates were different during those hours. Customers were randomly assigned to continue to get standard rates or to receive the time-of-day rate structure. Special meters were attached that recorded usage during peak and off-peak hours, which the customers could read. The technician who read the meter did not know what rate structure each customer had.

b. To test the effects of drugs and alcohol on driving performance, 20 volunteers were each asked to take a driving test under three conditions: sober, after two drinks, and after smoking marijuana. The order in which they drove under each condition was randomized. An evaluator watched them drive on a test course and rated their accuracy on a scale from 1 to 10, without knowing which condition they were under each time.

c. To compare four brands of tires, one of each brand was randomly assigned to the four locations on each of 50 cars. These tires were specially manufactured without any labels identifying the brand. After the tires had been on the cars for 30,000 miles, the researchers removed them and measured the remaining tread.