20 Quota sampling is a method used when. for example, an interviewer stands at a street corner and conducts interviews until obtaining a quota in various categories representing the relative sizes of various groups in the population of interest For instance, the quota might be 50 factory workers, 100 housewives. 60 elderly people. 30 blacks and so forth.

a) Is this a probability of nonprobability sampling method? Explain, and discuss polcotial advantages or disadvantages of this method. (Even professional pollsters such as Gallup used this method until 1948. when they incorrectly predicted that Dewey would defeat Truman in a landslide in the presidential election)

b) Explain how quota sampling differs from (i) cluster sampling, fii) stratified sampling.