Multistage Sample: Useful when individuals are at the bottom of a sequence of categories: E.g. to choose a sample of college women, first select 10 colleges, at random, then from those colleges select 2 dorms at random, then from each dorm select 10 students to interview. Total sample = 200. Advantage: you only have to visit 10 colleges, 2 dorms in each. An SRS from the whole country, even if you could do it, might mean 200 colleges. (You can also mix this with stratification, for instance selecting the 10 colleges in a stratified way from large coed, small coed, womens,...)
Systematic Random Sample (p.184,
problem
3.27) Using a list, to pick a sample of 1/20 of the list: First
pick
a number at random from 1,2,....20. Suppose you get 8. The
8th individual in the list is the first one in the sample. Then
take
every 20th individual after that, numbers 28, 48, 68,....
Advantage:
Easy to implement, avoids "clumps" that might occur with SRS.
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