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Computation of Base Weights for the 2007 Assessment
Every sampled school and student received a base weight equal to the reciprocal of its probability of selection. The details of how the school base weight was computed vary by whether the school was an original school (i.e., selected from either the public or private school frame), a new school, or a substitute school.
Computation of a student base weight reflects
the student's overall probability of selection accounting for school and student sampling;
assignment to session type
at the school- and student-level; and
the student's assignment to the mathematics, reading, or writing assessment.
Last updated 28 August 2009 (JL)