Within each sampled school, a sample of students was selected from a listing of the students in the grade such that every student had an equal chance of selection. The student lists were submitted in multiple ways. E-Filing is an electronic submission system. Excel files are submitted for sampled schools by school coordinators or NAEP State Coordinators. Files can be submitted for one school at a time or for an entire jurisdiction at once. This method allows schools to easily submit student demographic data electronically with the student lists, easing burden on NAEP field supervisors and school coordinators. Schools that are unable to submit their student lists using the E-Filing system provide hard-copy lists via the student listing form to NAEP field supervisors. In 2005, some 15,585 schools e-filed their student lists, while 2,425 were submitted using the student listing form.
In year-round, multi-track schools, students who are not scheduled to be in school on the assessment day are removed from the student lists prior to sampling. Student base weights were adjusted to account for these students.
The sampling process was the same regardless of list submission type. The sampling process was systematic (e.g., if the sampling rate was 1/2, a random starting point of one or two was chosen, and every other student on the list was selected). For e-filed schools only, where demographic data is submitted for every student on the frame, students are sorted by sex and race before the sample is selected to implicitly stratify the sample. Race and sex are provided for all but 2.6% of e-filed students.
In the certainty jurisdictions, all students were sampled in all schools. Otherwise, the average sample size was 60 students per hit for schools conducting the reading-mathematics assessments, and 90 students for those accepting reading-mathematics-science assessments. Larger schools may have been hit more than once in the sampling process and thus may have a larger sample size. In addition, most fourth-grade schools chose the option of taking all students when enrollment was between 60 and 120, rather than 60 or 90 of the original selection. This increased the fourth-grade sample size in many states beyond the designated target.
Some students enrolled in the school after the sample was selected. In such cases, new enrollees were sampled at the same rate as the students on the original list.
Students in reading-mathematics-science jurisdictions were randomly assigned to a reading, mathematics, or science assessment with 1/3 probability of getting each subject. Students in reading-mathematics-only jurisdictions were randomly assigned to a reading or mathematics assessment with 1/2 probability of getting each subject. This was implemented by spiraling: the booklets assigned to sampled students were provided from booklet packets which had, on average, equal numbers of each of the relevant assessments in a randomized order.
Some students were excluded because they are English language learners or have a disability. Excluded students were removed from the assessment sample.