Figure 8.1: Domain of Behavioral Science Statistics

An academic discipline such as Basic Math, Algebra, or Statistics is represented as
a particular set of problems or questions that comprehensively
embody the knowledge of the discipline. That set is called
the domain, and the problems are called
items. A symbolic representation of the domain
of Behavioral Science Statistics uses dots standing for items
(Fig. 8.1). One of the items, which might
be entitled "Word problem with percentages," is indicated by a line. The problem in the
rectangle is an instance of that item.

Each item, or problem type, has at least dozens, more often hundreds or
thousands of instances. Full mastery of the subject implies the ability to
solve problems corresponding to all the items making up the domain.

Determining the set of items that make up the domain is the first step
in constructing a "knowledge structure" for that domain. This is
done by research in instructional materials and standards and systematic
consultation with professionals. Substantial agreement is achieved among
expert pedagogues on the choice and definition of items. The set of items
finally arrived at and forming the domain must be comprehensive, that
is, it must cover all the concepts that are included in the particular
academic discipline.

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