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NAEP Assessment Weighting Procedures → Weighting Procedures for the 2006 Assessment → Computation of Full-Sample Weights for the 2006 Assessment → Computation of Base Weights for the 2006 Assessment → School Base Weights for the 2006 Assessment

NAEP Technical DocumentationSchool Base Weights for the 2006 Assessment

			Substitute public school Substitute private school

The school base weight for a sampled school is equal to the inverse of its probability of selection. The computation of the school base weight differs by whether the school was an original (i.e., selected from the public or private school frame) or a substitute school.

The school base weight for an originally selected school is equal to the inverse of its overall probability of selection. The school overall probability of selection is equal to the product of two quantities:

• the probability of selection of the primary sampling unit (PSU), and
• the probability of selection of the school within the selected PSU from the NAEP public school frame or private school frame. 

A school that takes the place of a refusing original school is known as a "substitute school." A substitute school is treated as if it were the original school that it replaced, and so is assigned the school base weight of the original school.

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