Question：A company wishes to carry out a national survey of adults' reading habits. To reduce travelling costs, the country was divided into constituencies. A sample of 50 constituencies was selected at random. With each of these constituencies, 5 polling districts were selected, again using random techniques. Interviewers will visit a random selection of 30 people on the electoral register of each district selected.
What sampling method is the company using?
A. Stratified
B. Systematic
C. Multi-stage
D. Simple random
The correct answer is: C
The sample is selected in stages, at first selecting not individuals but constituencies.
Multi-stage sampling is the correct answer as this method involves dividing the population into a number of sub-populations and then selecting a small sample of these sub-populations at random. Each sub-population is then divided further.
Stratified sampling involves dividing the population into strata and then taking a random sample from each stratum.
Random sampling is where every member of the population has an equal chance of being selected and systematic where every nth item after a random start is selected.
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