Title: The Apriori Algorithm as an Engine for Computerized Adaptive Assessment Author: Niels Smits Affiliation: Abstract: Both in medical research and clinical practice, questionnaire-based assessments are increasingly used to obtain information about patients. Such information is often used to make clinical predictions, classifying respondents into categories, such as `at risk' and `not at risk' for pathology. An important consideration in designing questionnaires is to minimize respondent burden, and computerized assessment provides an opportunity to make test administration efficient. For questionnaires meeting certain measurement properties, adaptive testing algorithms have been developed which not only allow for early stopping, but also for the dynamic selection of items to minimize testing time. By contrast, questionnaires not meeting such standards, such as those assessing symptomatology, do not allow for this methodology, and therefore alternative methods are needed. In the current study it is illustrated how the apriori algorithm, commonly used in market basket analysis, may be utilized as a method for computerized adaptive testing.