In considering which variables to use in creating national linking weights, there are two important requirements:
Self-assessment of the student's proficiency level in the domain being assessed proves to be an excellent item for this purpose. It is strongly correlated with proficiency in NAEP, and the form of the question and student's response would not be affected by whether the student is participating in a state-by-state or national assessment component.
The student's response to the question "I am good at math" (agree, undecided, disagree) determines grade 4 mathematics skill. The class in which the student was enrolled determines grade 8 mathematics skill: eighth-grade mathematics, pre-algebra, first-year algebra, other.
The definition of science skill level was redefined for the 2000 assessment. In 1996, grade 4 was defined by self-assessment; grade 8 by the class in which the student was enrolled (earth science, physical science, life science, general science, integrated science, other, none). The distribution of science course enrollment changed in 2000. Higher proportions of students enrolled in general science and integrated science and a lower proportion enrolled in physical science. Since the relation of science course enrollment to student ability could not be confirmed, science skill level was defined by self-assessment. Therefore, for the 2000 assessment, both grade 4 and 8 were determined by the answer to the question "I am good at science" (agree, not sure, disagree).