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 onSaturday or (2) having extended branch hours during the week. Listed below are some of theideas proposed for gathering data. For each, indicate what (if any) biases (problems) mightresult.
a) Put a big ad in the newspaper asking people to log their opinions on the bank'sWeb site.
b) Randomly select one of the branches and contact every customer at that bank byphone.
c) Send a survey to every customer's home, and ask the customers to fill it out andreturn it.
d) Randomly select 20 customers from each branch. Send each a survey, and followup with a phone call if he or she does not return the survey within a week.