NAEP Technical DocumentationComponents of Subject-Specific School Base Weights

PSU Weight

The primary sampling unit (PSU) weight, PSUWGT_M, is the reciprocal of the probability of selection for the PSU. In all national main 2000 assessment samples except the grade 8 public school sample, 94 PSUs were selected; 22 were certainty PSUs and 72 were noncertainty PSUs. Certainty PSUs, which have 100 percent chance of selection, have a PSU weight of 1.0. PSU weights for the noncertainty PSUs reflect a probability proportional to size (PPS) sampling scheme with one PSU per stratum. The grade 8 public school sample did not involve PSU selection except in sparse states. Schools in nonsparse states were assigned PSU weights of 1.0, while schools in sparse states were assigned PSU weights reflecting PPS sampling.

PSS Weight

The weight RSCHWT is the reciprocal of the probability of inclusion of a private school on the Private School Survey (PSS) file, the source of the national main NAEP private school frame. Public schools, which are not part of the PSS study, were assigned a PSS weight of 1.0.

School Weight

The school weight, SCH_WT, is the reciprocal of the probability of selection of the school conditional on the primary sampling unit.

Subject Assignment Weight

The subject assignment weight, ASBJWT, is the reciprocal of the probability that the particular subject was assigned to the school. Subject assignment weights are calculated separately for grade, subject, and school type. The weight is a function of the subject and number of sessions assigned to the school for public schools and subject, number of subjects assigned to the school, and religious affiliation from the school frame (FRMTYP) for private schools. The first table below summarizes the values of the weight for public schools, while the second table summarizes the values of the weight for private schools. Note that the weights for public schools are presented in terms of number of sessions, and the weights for private schools are presented in terms of number of students. However, the ratios (the weights themselves) are what are important, not the magnitudes of the numerators and denominators. The subject assignment weights reflect dropped subjects or sessions in schools where enrollment is smaller than expected for the given grade.

Subject assignment weights (ASBJWT) for public schools, by grade and number of sessions assigned, national main assessment: 2000
Grade	Number of sessions assigned	Mathematics	Science	Reading
4	1	29/7	29/9	29/6
	2	29/14	29/18	29/12
	3	29/21	29/24	29/18
	4	29/28	1	29/24
8	1	2	2	†
8	2	1	1	†
12	1	16/7	16/9	†
12	2/3/4	1	1	†
† Not applicable; the 2000 reading assessment was not administered at grade 8 or 12. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2000.

Subject assignment weights (ASBJWT) for private schools, by grade, number of sessions assigned, and religious affiliation, national main assessment: 2000
Grade	Number of sessions assigned	Religious affiliation	Mathematics	Science	Reading
4	1	Catholic	7,650/3,000	7,650/3,000	7,650/1,110
		Lutheran	1,650/750	1,650/750	1,650/90
		Conservative Christian	1,890/750	1,890/750	1,890/270
		Other religious	1,920/750	1,920/750	1,920/270
		Nonsectarian	1,740/750	1,740/750	1,740/150
		NAIS¹ members	1,680/750	1,680/750	1,680/120
		Unknown	16,530/6,750	16,530/6,750	16,530/2,010
	2	Catholic	7,650/6,000	7,650/6,000	7,650/2,220
		Lutheran	1,650/1,500	1,650/1,500	1,650/180
		Conservative Christian	1,890/1,500	1,890/1,500	1,890/540
		Other religious	1,920/1,500	1,920/1,500	1,920/540
		Nonsectarian	1,740/1,500	1,740/1,500	1,740/300
		NAIS¹ members	1,680/1,500	1,680/1,500	1,680/240
		Unknown	16,530/13,500	16,530/13,500	16,530/4,020
8	1	Any religious affiliation	2	2	†
8	2	Any religious affiliation	1	1	†
12	1	Any religious affiliation	2	2	†
12	2	Any religious affiliation	1	1	†
† Not applicable; the 2000 reading assessment was not administered at grade 8 or 12. ¹ NAIS is the National Association of Independent Schools. SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2000.

Sample Type Weight

The sample type weight, STYWT, reflects the splitting of the school sample for each grade into two equal size subsets (S2 and S3) for analysis by two different sets of administration rules by subject. Each school was assigned a sample type weight of 2.0.

Last updated 17 June 2008 (MH)

Printer-friendly Version