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 | | Sampling from the frame was done in a way that ensured the sample would include specified numbers of schools from each superstratum and substratum. |
 | | The number of substrata within public superstrata varies superstratum to superstratum, but never exceeds four. |
 | | For example, in the Public, New York superstratum there are four substrata: minority, urban, nonminority, suburban, nonminority, rural, and nonminority. |
| www.stat.ucla.edu /data/nels/deborah-and-amy/thoughts2 (2198 words) |
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