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NAEP Weighting Procedures → 2002 Weighting Procedures and Variance Estimation → National Main Assessment Weights → Computation of Base Weights → Computation of Student Base Weights

NAEP Technical DocumentationComputation of Student Base Weights

The student base weight is assigned to every student sampled to receive a 2002 national main assessment, whether or not the assessment took place. The student base weight, in a sense, reflects the number of students that the sampled student represents in the population for purposes of estimation. The summation of the student base weights over a particular student group is an unbiased estimate of the total number of students in that student group in the population. (This assumes that the school nonresponse adjustments completely adjusted for bias due to school nonresponse.)

The student base weight STUWGT_sk (school s, student k) is a product of the following factors:

• the school base weight (the inverse of the school's probability of selection);

• the session allocation weight, i.e., the inverse of the probability that the school is assigned at least one “A” session SCHSES_s^(A);

• the school nonresponse adjustment factor SNRADJ_c;

• the substitution adjustment factor to account for the difference in size between the substitute and its corresponding original school SUBADJ_s;

• the school trimming factor TRIM_s;

• the within-school sampling interval for student selection WINSCHL_s;

• the inverse of the probability that the student was assigned to the “A” session SES_sk^(A); and

• a factor for year-round schools YRRND_s.

To summarize:

STUWGT_sk = × SCHSES_s^(A) × SNRADJ_c × SUBADJ_s × TRIM_s × WINSCHL_s × SES_sk^(A) * YRRND_s

The Field trial and equating studies sample design for session assignments determines the values of SCHSES_s^(A) and SES_sk^(A). School nonresponse adjustment SNRADJ_c is done separately for each session type. The special school weighting factors include the substitute school weighting factor SUBADJ_s and school trimming factor TRIM_s. The within-school sampling interval WINSCHL_s is the inverse of the overall student sampling rate in the school. The year-round school factor YRRND_s adjusts for students who do not attend school during the time of the assessment in year-round schools.

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