A bank with branches in a large metropolitan area is considering opening its offices on Saturday, but it is uncertain whether customers will prefer (1) having walk-in hours on Saturday or (2) having extended branch hours during the week. Listed below are some of the ideas proposed for gathering data. For each, indicate what kind of sampling strategy is involved and what (if any) biases might result.
(a) Put a big ad in the newspaper asking people to log their opinions on the bank’s Web site.
(b) Randomly select one of the branches and contact every customer at that bank by phone.
(c) Send a survey to every customer’s home, and ask the customers to fill it out and return it.
(d) Randomly select 20 customers from each branch. Send each a survey, and follow up with a phone call if he or she does not return the survey within a week.