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Computation of Base Weights for the 2005 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 varies 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;
the school and student assessment type assignment (operational assessment or bridge study); and
the student's assignment to the mathematics, reading, or science assessment.
Last updated 17 April 2009 (JL)