NAEP Technical DocumentationCalculation of Replicate Weights

Defining Replicate Strata and Forming Replicates

Computing School-Level Replicate Weights

Computing Student-Level Replicate Weights

In addition to the full-sample weight, a set of replicate weights was provided for each student. These replicate weights are used in calculating the sampling variance of estimates obtained from the data, using the jackknife repeated replication method. The method of deriving these weights was aimed at reflecting the features of the sample design appropriately in each jurisdiction, so that when the jackknife variance estimation procedure is implemented, approximately unbiased estimates of sampling variance are obtained. This page gives the specifics for generating the replicate weights for the 2003 assessment samples.

Schools were assigned to replicate strata separately for the following samples: fourth- and eighth-grade public schools by grade and jurisdiction, and fourth- and eighth-grade private schools by grade. All sampled schools were assigned to replicate strata, not just participating or eligible schools. In states with Trial Urban District Assessment (TUDA) samples or special charter school samples at grade 4, replicate strata were assigned at the same time for all sampled schools in the state.

In each sample, replicates were formed in two steps. First, each school was assigned to one or more of 62 replicate strata. In the next step, a random subset of schools (or, in some cases, students within schools) in each replicate stratum was excluded. The remaining subset and all schools in the other replicate strata then constituted one of the 62 replicates.

The computation of replicate weights includes

defining replicate strata and forming replicates;
computing school-level replicate weights;
computing student-level replicate weights; and
trimming student replicate weights.

Last updated 06 November 2008 (RF)

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