## Computing Student-Level Replicate Base Weights for the 2007 Assessment

The calculation of the student-level replicate base weights differed by whether a student was in a school selected with certainty or not, since replicates were formed using first-stage sample units. The first-stage sample unit was the student in certainty schools and the school itself for noncertainty schools.

For students in certainty schools, where replicate strata were formed at the student-level by grouping students into pairs or triplets, student base weights were calculated for each of the 62 replicates based on this grouping. For students in replicate strata comprising pairs of students, the student-level replicate base weights, STU_BWTjsk(r), r = 1,..., 62, were calculated as follows:

where

• STU_BWTjsk is the full-sample student base weight for student k in certainty school s in stratum j,

• Rjsr is the set of students within the r-th replicate stratum for certainty school s in stratum j, and

• Ujsk is the variance unit (1 or 2) for student k in certainty school s in stratum j.

For students in replicate strata comprising three students, two sets of student-level replicate base weights were computed (see replicate variance estimation for details): one for the first replicate r1 and another for the second replicate r2. The two sets of student-level replicate base weights STU_BWTjsk(r1), r1 = 1,..., 62 and STU_BWTjsk(r2), r2 = 1,..., 62 were calculated as described below.

where

• STU_BWTjsk is the full-sample student base weight for student k in certainty school s in stratum j,
•   is the set of students within the r1-th replicate stratum for certainty school  s in stratum j,
• is the set of students within the r2-th replicate stratum for certainty school s in stratum j, and
• Ujsk is the variance unit (1, 2 or 3) for student k in certainty school s in stratum j.

For students in noncertainty schools, where replicate strata were formed at the school-level, the student base weight for student k from school s in stratum j for each of the 62 replicates STU_BWTjsk (r), r = 1,..., 62, were calculated as follows:

where

• SCH_BWTjs(r) is the replicate school base weight;

• SCHSESWTjs is the school-level session assignment weight used in the full-sample weight;

• WINSCHWTjs is the within-school student sampling weight used in the full-sample weight;

• STUSESWTjsk is the student-level session assignment weight used in the full-sample weight;

• SUBJFACjs is the subject factor used in the full-sample weight;

• SUBADJjs is the substitute adjustment factor used in the full-sample weight; and

• YRRND_AFjs is the year-round adjustment factor used in the full-sample weight.

Last updated 19 May 2010 (GF)