NAEP Assessment Sample Design → NAEP 2008 Sample Design → 2008 Long-Term Trend (LTT) Assessment Sample Design → 2008 Public School Long-Term Trend (LTT) Assessment → Sampling Frame for the 2008 Public School Long-Term Trend (LTT) Assessment

NAEP Technical DocumentationSampling Frame for the 2008 Public School Long-Term Trend (LTT) Assessment

The sampling frame for public schools was derived from the Common Core of Data (CCD) file corresponding to the 2004-05 school year. The CCD files provided the frame for all regular public, state-operated public, Bureau of Indian Education (BIE), and Department of Defense Domestic Dependent Elementary and Secondary Schools (DDESS) open during the 2004-05 school year. 

The sampling frame was restricted to schools located in the primary sampling units (PSUs) selected for the 2008 long-term trend (LTT) assessment. In addition, the sampling frame excluded ungraded schools, vocational schools with no enrollment, special education-only schools, prison and hospital schools, home-school entities, virtual or online schools, and juvenile correctional institutions.

The following table presents the number of schools and estimated enrollment for the public school LTT frame by age population. The unweighted school count is restricted to the selected PSUs. The estimated enrollment incorporates the PSU weight (inverse of the probability of selecting the PSU) and the estimated age-eligible enrollment, and thus is a national estimate of the number of public school students in the age population. The age-eligible enrollment was estimated using age distribution fractions derived for each grade associated with the age range.

Number of schools and enrollment in public school frame, long-term trend (LTT) assessment, by age: 2008

Age	School count in sampled primary sampling units (PSUs)	Estimated enrollment (unweighted)	Estimated enrollment (weighted)
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008 Long-Term Trend Assessment.
9	22,050	1,730,480	3,655,779
13	19,739	1,748,623	3,766,800
17	7,461	1,638,967	3,509,971

For quality control purposes, school and student counts from the sampling frame were compared to school and student counts from the NAEP LTT 2004 frame. No major discrepancies were found.

New-School Sampling Frame for the Long-Term Trend Assessment

The CCD file used for the frame corresponds to the 2004-05 school year, whereas the assessment year is the 2007-08 school year. During this 3-year period, some schools closed, some changed structure (e.g., grade span changed or one school became two schools), and others came into existence.

To achieve as close to full coverage as possible, the LTT school frame was supplemented by a sample of new schools obtained from districts associated with the LTT PSUs. The first step in this process was the development of a new-school frame through the construction of a district-level file from the CCD school-level file. Since asking every school district to list new- and newly-eligible schools would have generated too much of a burden, the following strategies were implemented:

• The New Schools Procedure was not implemented in small districts. A district was considered small if no individual grade was offered by more than one school. The burden that would have been imposed on the small districts was judged to be too great for the slight improvement in coverage expected from including new schools from such districts.
• A sample of (non-small) districts was selected and each sampled district was sent a list of the CCD schools and asked to add in any new schools or old schools that had become newly eligible. To represent the unsampled districts in the full sample of schools, weights for schools included in the new-school sample were adjusted to reflect the district selection probability.
• The New Schools Procedure for charter-only and state-run schools was implemented only in states where more than 60 percent of youths fell within LTT sampled PSUs. This cutoff was necessary for the following reasons. Typically, NAEP State Coordinators are asked about all new charter-only and state-run schools. These types of school districts tend not to be geographically compact; therefore, linking such a district to a single LTT PSU  is infeasible, except at the individual school level. The smaller the proportion of a state’s population falling within sampled LTT PSUs, the less likely that a specific new school of this type would be added to the frame and the more likely the state would be burdened by the process.

      

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