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Variables That Define Groups in NAEP

The variables used to define groups for a given assessment scale (or group of scales) include a broad spectrum of background and experiential variables and composites of such variables. All standard reporting variables are used in the population-structure models. Results for any variables not used in the models may be biased.

The initial step in construction of variables used in the scale score distribution models involves forming student-based vectors of response data from answers to student, teacher, and school questionnaires, demographic and background data, and other student information known prior to scaling.

The initial vectors concatenate this student background information into a series of identifying "contrasts" comprising the following variables and interactions:

  • Categorical variables are derived by expanding the response options of a questionnaire variable into a binary series of one-degree-of-freedom "dummy" variables or contrasts. These form the majority of variables in the vector.
  • Demographic variables possess ordinal response options, such as number of hours spent watching television, which are included as linear and/or quadratic multi-degree-of-freedom contrasts. However in 2002 and 2003 assessments, linear multi-degree-of-freedom contrasts were replaced by binary series of one-degree-of-freedom "dummy" contrasts, and quadratic multi-degree-of-freedom contrasts were removed.
  • Continuous variables, such as student enrollment in a school or in a grade within a school, are included as contrasts in their original form or a transformation of their original form.
  • Interactions of two or more categorical variables form a set of orthogonal one-degree-of-freedom dummy variables or contrasts.

The specifications used for constructing the variables used in the scale score distribution models are provided, along with a summary. Starting in 2008 and continuing forward, the listing of estimation variables used in the population-structure models is presented in textual format. For more information about NAEP variables, see lists of each variable available by assessment year and subject.

Links to summary tables of the estimation variables used to define groups in NAEP: 2000–2008
Year Subject area
2008 Arts
Mathematics long-term trend
Reading long-term trend
2007 Mathematics
2006 Civics
U.S. history
2005 Mathematics
2004 Mathematics long-term trend
Reading long-term trend
2003 Mathematics
2002 Reading
2001 Geography
U.S. history
2000 Mathematics
SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP), Various Years, 2000–2008 Assessments.

Last updated 15 June 2010 (JL)
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National Center for Education Statistics -
U.S. Department of Education