A spiral is the smallest set of booklets that accomplishes the test booklet distribution goals. By utilizing this method, NAEP can sample enough students to obtain precise results for each test question while generally consuming an average of about an hour and a half of each student's time. Following is an example of a balanced incomplete block (BIB) booklet design using five blocks (A–E). In this design, each cognitive block appears twice in each of the two possible positions, and each block is paired once with every other block (see Messick, Beaton, and Lord 1983).
|SOURCE: U.S. Department of Education, Institute of Education Sciences, National Center for Education Statistics, National Assessment of Educational Progress (NAEP).|
The booklet numbers also represent the spirals (1 through 10).
For some assessments, NAEP uses a variation of the BIB booklet design—the pBIB, or partially balanced incomplete block design.
The next step is designing a bundling scheme with this spiral.