 ... or the 1970 Census data by counties. Within each final stratum, four schools were selected, and then two of the four were randomly designated as the primary selections. The other two schools were retained as backup or substitutes and used in the sample...  School File Documentation - Page 2by Louise B. Henderson - 1981 - 95 pagesFull view - About this book
 | Research Triangle Institute - College students - 1977 - 92 pages
...retained as backup or substitutes and used in the sample only if one or both of the primary schools did not cooperate. The second stage of the sampling procedure...drawing a simple random sample of 18 students per school and then selecting 5 additional students as replacements for possible nonparticipants among the 18.... | |
 | National Center for Education Statistics - Educational surveys - 1978 - 866 pages
...retained as backup or substitutes and used in the sample only i one or both of the primary schools did not cooperate. The second stage of the sampling procedure consisted of first drawing simple random sample of 18 students per school and then selecting five addi tional ones as replacements... | |
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