Unlike most of the NAEP operational assessment, the population target for the long-term trend (LTT) assessment is defined by age rather than grade. The three age populations for the 2008 study are as follows:
The sample was designed to be nationally representative at each of these age populations. The target population included all students in these age ranges enrolled in public and private schools. The samples were selected based on a three-stage sample design:
The overall sample sizes were driven by the targeted number of students for each subject. The 2008 LTT subjects were
The target numbers of assessments are the same for each age group (9, 13, 17) as given in the following table.
|Public school students||Private school students||Total students|
|SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), 2008.|
These targets represent completed assessments. To get the overall sample sizes, these targets were adjusted upwards to allow for expected losses from absent, refusing, and/or ineligible schools and students (so that the completed assessment targets would be met). The corresponding overall students sample sizes are contained in the Participation, Exclusion, and Accommodation Rates pages.