Aş spune a two-stage conventional cluster (probability) sampling

For most target groups, two-stage sample designs were used i.e. primary units (clusters) chosen at the first stage and individual respondents chosen at the second stage. When members of the target group were associated with sites in a fixed manner, conventional clusters were used;
http://www.etharc.org/publications/bss/chap2.htm

In real-life surveys, it is common to have several levels of sampling, including use of stratification and ratio estimators. Here we will consider two-stage cluster sampling where a simple random sample of clusters is taken, then a simple random sample of elements in the selected clusters is taken.
http://www.webpages.uidaho.edu/~chrisw/stat422/TwoStageClust...



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Note added at 6 days (2009-12-14 08:28:43 GMT) Post-grading
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Cu plăcere,
G