if they are on pace to complete a timed test section. Test takers may thus be penalized for spending too much time on a difficult question which is presented early in a section and then failing to complete enough questions to accurately gauge their proficiency in areas which are left untested when time expires. While untimed CATs are excellent tools for formative assessments which guide subsequent instruction, timed CATs are unsuitable for high-stakes summative assessments used to measure aptitude for jobs and educational programs. Components There are five technical components in building a CAT (the following is adapted from Weiss & Kingsbury, 1984 ). This list does not include practical issues, such as item pretesting or live field release. Calibrated item pool Starting point or entry level Item selection algorithm Scoring procedure Termination criterion Calibrated item pool A pool of items must be available for the CAT to choose from. Such items can be created in the traditional way (i.e., manually) or through Automatic Item Generation. The pool must be calibrated with a psychometric model, which is used as a basis for the remaining four components. Typically, item response theory is employed as the psychometric model. One reason item response theory is popular is because it places persons and items on the same metric (denoted by the Greek letter theta), which is helpful for issues in item selection (see below). Starting point In CAT, items are selected based on the examinee's performance up to a given point in the test. However, the CAT is obviously not able to make any specific estimate of examinee ability when no items have been administered. So some other initial estimate of examinee ability is necessary. If some previous information regarding the examinee is known, it can be used, but often the CAT just assumes that the examinee is of average ability - hence the first item often being of medium difficulty level. Item selection algorithm As mentioned previously, item response theory places examinees and items on the same metric. Therefore, if the CAT has an estimate of examinee ability, it is able to select an item that is most appropriate for that estimate. Technically, this is done by selecting the item with the greatest information at that point. Information is a function of the discrimination parameter of the item, as well as the conditional variance and pseudoguessing parameter (if used). Scoring procedure After an