NAEP Technical DocumentationWeighting Procedures for the 2020 Assessment

			Computation of Full-Sample Student Weights Computation of Replicate Student Weights for Variance Estimation Computation of Full-Sample School Weights Computation of Replicate School Weights for Variance Estimation Quality Control on Weighting Procedures

NAEP assessments use complex sample designs to create student samples that generate population and subpopulation estimates with reasonably high precision. School and student sampling weights permit valid inferences from the school and student samples to their respective populations. In 2020, weights were developed for schools and students sampled at ages 9 and 13 for long-term trend assessments in reading and mathematics. Assessments at age 17 were not conducted due to the COVID-19 pandemic.

Student Weights

Each student was assigned a weight to be used for making inferences about students in the target population. This weight, known as the final full-sample student weight, contains six major components:

• the student base weight;
• school nonresponse adjustment;
• student nonresponse adjustment;
• school weight trimming adjustment;
  
• student weight trimming adjustment; and
• student raking adjustment.

The student base weight is the inverse of the overall probability of selecting a student and assigning that student to a particular assessment. The sample design that determines the base weights is discussed in the NAEP 2020 sample design section.

The student base weight is adjusted for two sources of nonparticipation: school level and student level. These weighting adjustments seek to reduce the potential for bias from such nonparticipation by

• increasing the weights of students from schools similar to those schools not participating, and
• increasing the weights of participating students similar to those students from within participating schools who did not attend the assessment session (or makeup session) as scheduled.

Furthermore, the final student weights reflect the trimming of extremely large weights at both the school and student levels. These weighting adjustments seek to reduce variances of survey estimates.

For some assessments, an additional weighting adjustment is implemented so that estimates for key student-level characteristics are in agreement across those assessments. This adjustment is implemented using a raking procedure.

In addition to the final full-sample student weight, a set of replicate weights was provided for each student. These replicate weights are used to calculate the variances of survey estimates using the jackknife repeated replication method.

The methods used to derive these weights were aimed at reflecting the features of the sample design. When the jackknife variance estimation procedure is implemented, approximate unbiased estimates of sampling variance are obtained. In addition, the various weighting procedures were repeated on each set of replicate weights to appropriately reflect the impact of the weighting adjustments on the sampling variance of a survey estimate.

School Weights

In addition to student weights, school weights were calculated to provide secondary users means to analyze data at the school level. The school weights are subject specific and are computed for the schools that contained at least one student that participated in the NAEP assessment for that subject. 

Each school was assigned a weight to be used for making inferences about schools in the target population. This weight, known as the final full-sample school weight, contains five major components:

• the school base weight;
  
• school nonresponse adjustment;
  
• school weight trimming adjustment; 
• school-session assignment weight; and
  
• small-school subject adjustment.
  

The school base weight is the inverse of the overall probability of selecting a school for a particular assessment. 

The school nonresponse adjustment increases the weights of participating schools to account for similar schools that did not participate, and the school trimming adjustment reduces extremely large weights to decrease variances of survey estimates. These two adjustments are the same school-level adjustments used in the final full-sample student weight described above. 

The school-session assignment weight reflects the probability that the particular session type was assigned to the school. For 2020 since there is only one session type, this adjustment is always one.

The small-school subject adjustment accounts for very small schools that did not have enough participating students for every subject intended for the school. School weights for subjects that had at least one eligible student are inflated by this factor to compensate for schools of the same size that did not have any eligible students for those subjects and would not be represented otherwise.

In addition to the final full-sample weight, a set of replicate weights was provided for each school. These replicate weights are used to calculate the variances of school-level estimates using the jackknife repeated replication method.

Quality Control Procedures

Quality control checks were implemented throughout the weighting process to ensure the accuracy of the full-sample and replicate school and student weights. See the Quality Control on Weighting Procedures link above for the various checks implemented and main findings of interest.

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