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Formation of Replicate Groups for Variance Estimation

The formation of replicate groups was done separately for two distinct groups:

  • students who were classified as students with disabilities or limited-English-proficient students—referred to in NAEP as SD/LEP students, and
     
  • students who were not classified in this way—non SD/LEP students.

Forming the replicate groups separately for SD/LEP and non SD/LEP groups was necessary, because the method for assigning replicate groups was different for certainty schools versus noncertainty schools, and because of the nature of the reporting populations. The R2 reporting population includes all of the non SD/LEP students, but only SD/LEP students in sessions in which accommodations were not offered. The R3 reporting population includes all of the non SD/LEP students, but only SD/LEP students in sessions in which accommodations were offered. Thus some SD/LEP students were left out of each reporting population. This means that certainty schools were treated as certainties when forming replicate groups for the non SD/LEP students, but these same certainty schools were treated as noncertainties when forming replicate groups for the SD/LEP students.

With the exception of schools in American Samoa, Guam, Virgin Islands and the Department of Defense Domestic Dependent Elementary and Secondary Schools (DDESS) grade 8, schools were, in general, assigned to replicates as follows: Noncertainty schools were first paired and then each pair was assigned to its own replicate group. Large certainty schools were assigned to two replicate groups each, and small certainty schools were assigned to one replicate group each.

Replicate group assignments for schools in American Samoa, Guam, Virgin Islands and DDESS grade 8 were handled differently because of small sample sizes. For American Samoa, Guam, Virgin Islands and DDESS grade 8, schools were assigned to a number of replicate groups proportional to the estimated grade-specific enrollment.

Once replicate groups were formed for all schools, students were assigned to their respective school replicate groups.


Last updated 07 March 2008 (TK)

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National Center for Education Statistics - http://nces.ed.gov
U.S. Department of Education