Four sampling strategies have been proposed to help a bank determine whether customers favour opening on Saturdays versus keeping branches open longer during the week. For each, discuss what kind of sampling strategy is involved and what (if any) biases might result.
(a) sponsor a commercial during a TV program, asking people to dial one of two phone numbers to indicate which option they prefer.
(b) Hold a meeting at each branch and tally the opinions expressed by those who attend the meetings.
(c) Randomly select one day at each branch and contact every customer who visits the branch that day.
(d) Go through the bank's customer records, selecting every 100th customer. Hire a survey research company to interview the people chosen.