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Poststratification Procedures

        

Poststratification Adjustments, Geography

Grade 4 (Accommodations Not Permitted [R2])
Grade 4 (Accommodations Permitted [R3])
Grade 8 (Accommodations Not Permitted [R2])Grade 8 (Accommodations Permitted [R3])
Grade 12 (Accommodations Not Permitted [R2])
Grade 12 (Accommodations Permitted [R3])

Poststratification Adjustments, U.S. History

Grade 4 (Accommodations Not Permitted [R2])
Grade 4 (Accommodations Permitted [R3])
Grade 8 (Accommodations Not Permitted [R2])
Grade 8 (Accommodations Permitted [R3])
Grade 12 (Accommodations Not Permitted [R2])
Grade 12 (Accommodations Permitted [R3])

The poststratification adjustment procedure involved applying a ratio adjustment to the student reporting weights. Assessed and excluded students were partitioned into poststratification cells, and a single ratio adjustment factor was calculated and applied to the reporting weight of all students in a given cell. The numerator of the poststratification factor was an independent estimate of the number of students in the given cell, and the denominator was the corresponding estimate derived using the student reporting weights. The numerator was derived from 1998 and 1999 CPS data and 2000 population projections made by the U.S. Census Bureau.

The poststratification procedure was carried out separately by grade, assessment a=H,G, and reporting population R=2,3. Poststratification adjustment cells h were defined in terms of race, ethnicity, modal age status (modal age, not modal age), and Census region for all grades except grade 12. Modal age status was not used for grade 12 because it is not possible to derive reliable modal age status counts from the CPS data. CPS counts all adult education students, regardless of age, as grade 12 students. Instead, grade 12 used poststratification cells defined by students less than or equal to modal age (i.e., 17 years of age or younger).

The set of students taking assessment a in poststratification cell h is written as Cha. For grade 12, the set of students who are also 17 or younger (and therefore used in the computation of the poststratification factor) will be written as C'ha. For fourth and eighth grades Cha and C'ha are the same.

The poststratification factor for student ij taking assessment a, for reporting population R=2,3, in a given poststratification adjustment class h is given by

RPTPS_AD sub h a R equals TOTAL sub h divided by summation over C prime sub h a of open paren prew sub i j times REPF sub i j R closed paren

where

TOTALh = the total number of grade-eligible students in poststratification cell h from Census Bureau data
REPFijR = the reporting factor for student ij for reporting population R
prewij = the pre-poststratification student weight (see Trimming the Nonresponse Adjusted Student Weights)

Students at grade 12 who were age 18 or older received the poststratification factor according to their poststratification cell and subject even though they were not used in calculating the factor.

The final student-level weights after poststratification are

w sub i j R equals RPTPS_AD sub h a R times prew sub i j times REPF sub i j R for i and j elements of C sub h a

Last updated 26 August 2008 (FW)

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National Center for Education Statistics - http://nces.ed.gov
U.S. Department of Education