Shortening Affect Scales for Ambulatory Assessment: A Comparison of Different Item Response Theory-Based Approaches.

Researchers often seek to measure affective experiences in daily life. Consequently, measures of positive and negative affect frequently take up large parts of ambulatory questionnaires. Optimizing questionnaire content and length is crucial in intensive ambulatory studies. In the current study, we developed and tested approaches to shortening ambulatory affect questionnaires. Specifically, we built a preliminary item bank of 14 positive and 20 negative affect items calibrated with a graded response model using data from 14 individual ambulatory assessment studies (N = 3,818). We then compared different item response theory-based strategies for shortening affect questionnaires to two to four items in simulation studies. The results indicate that not only computerized adaptive testing but also simpler (semi-)static item selection strategies achieve higher precision with the same number of items compared to random selection. We provide concrete recommendations and highlight issues encountered and avenues for further refinement of the item bank.