Question: Suppose that Ralph would execute his study in the way that he has proposed. Suppose that 109 persons would return his questionnaire and that, for various reasons, 12 of these questionnaires are not useful. Furthermore, suppose that analysis of the data would reveal that 56% percent of the participants are customers of a bank that came through the crisis quite well; this particular bank has taken little risks with its customers' money and has not needed any support from the government.
Do you think that Ralph's sample is large enough?
How may the fact that 56% of the consumers is a customer of a very responsible bank affect the validity and/or reliability of the findings of Ralph's study? Is there anything that Ralph can do to solve these problems?