Аннотация:Missing data occur for a variety of reasons. Particularly problematic are those items anindividual skipped or could not reach in time. This article focuses on the practical effectsof using different statistical treatments with omitted and not-reached items in an itemresponse theory application. The particular strategy that is selected for scoring suchitems has a considerable impact on the interpretation of results. This impact is evident foreither individual results or group-level assessments.