A mortgage lender routinely places advertisements in a local newspaper. The
advertisements are of three different types: one focusing on low interest
rates, one featuring low fees for first-time buyers, and one appealing to
people who may want to refinance their homes. The lender would like to
determine which advertisement format is most successful in attracting
customers to call for more information. Describe an experiment that would
provide the information needed to make this determination. Be sure to consider
extraneous factors, such as the day of the week that the advertisement appears
in the paper, the section of the paper in which the advertisement appears, or
daily fluctuations in the interest rate. What role does randomization play in
your design?