ABSTRACT
Test theory is the “collection of mathematical concepts that formalize and clarify certain questions about constructing and using tests, and then provide methods for answering them" (McDonald, 1999, p. 9). The two primary components of the theory are the test and the persons responding to the test. A test is a set of items that are intended to relate to some unobservable mental trait. A test, also referred to as a survey, scale, or instrument in various contexts, may be used to measure achievement, knowledge, aptitude, psychological traits, or attitude. Just as a ruler is used to measure length or a protractor to measure an angle, a test is used to measure a latent trait. Items that make up a test may be dichotomous, or binary, when there are only two response options, e.g., correct or incorrect, yes or no, etc. Items with more than two response options are polytomous, e.g., a Likert style response scale, multiple-choice responses, or partial-credit Scoring.
