A leading manufacturer of ladies' lingerie has maintained its high share in the pantyhose market over the past five years but has experienced a dramatic decrease in sales. This has led Cheryl Martin, the VP of marketing, to conclude that the market for pantyhose as a whole must be shrinking. In an effort to determine whether a shift in women's attitudes or lifestyles is responsible for the shrinkage of the market for pantyhose, she has decided to conduct a nationwide telephone survey of women across the country.
a. How can the adoption of a random assignment procedure help maintain the internal validity of the experiment?
b. Suggest a randomization technique that would be appropriate for this study.