The 2001 assessment sampling plan included a random assignment of the sampled students within each school to a geography assessment or a U.S. history assessment. This assignment process was implemented by spiraling. The sampled students were handed booklets from a set of booklets that included the specified numbers of U.S. history and geography assessments.
The ratios of U.S. history to geography booklets in each booklet set was 1:1 for fourth grade, 5:4 for eighth grade, and 5:4 for twelfth grade. In any given school, especially schools with small sample sizes of students, the actual realized ratio of students assigned to geography or U.S. history varied from the desired ratio.