with issues of sampling—sampling of the content domain and of the student population.

The tasks on any particular assessment are supposed to be a representative sample of the knowledge and skills encompassed by the larger content domain. If the domain to be sampled is very broad, which is usually the case with large-scale assessments designed to cover a large period of instruction, representing the domain may require a large number and variety of assessment tasks. Most large-scale test developers opt for having many tasks that can be responded to quickly and that sample broadly. This approach limits the sorts of competencies that can be assessed, and such measures tend to cover only superficially the kinds of knowledge and skills students are supposed to be learning. Thus there is a need for testing situations that enable the collection of more extensive evidence of student performance.

If the primary purpose of the assessment is program evaluation, the constraint of having to produce reliable individual student scores can be relaxed, and population sampling can be useful. Instead of having all students take the same test (also referred to as “census testing”), a population sampling approach can be used whereby different students take different portions of a much larger assessment, and the results are combined to obtain an aggregate picture of student achievement.

If individual student scores are needed, broader sampling of the domain can be achieved by extracting evidence of student performance from classroom work produced during the course of instruction (often referred to as “curriculum-embedded” assessment). Student work or scores on classroom assessments can be used to supplement the information collected from an on-demand assessment to obtain a more comprehensive sampling of student performance. Although rarely used today for large-scale assessment purposes, curriculum-embedded tasks can serve policy and other external purposes of assessment if the tasks are centrally determined to some degree, with some flexibility built in for schools, teachers, and students to decide which tasks to use and when to have students respond to them.

Curriculum-embedded assessment approaches afford additional benefits. In on-demand testing situations, students are administered tasks that are targeted to their grade levels but not otherwise connected to their personal educational experiences. It is this relatively low degree of contextualization that renders these data good for some inferences, but not as good for others (Mislevy, 2000). If the purpose of assessment is to draw inferences about whether students can solve problems using knowledge and experiences they have learned in class, an on-demand testing situation in which every student receives a test with no consideration of his or her personal instruction history can be unfair. In this case, to provide valuable evidence of learning, the assessment must tap what the student has had the opportunity to learn (NRC, 1999b). In contrast to on-demand assessment, embedded



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