Objective: The purpose of this study is to describe the psychometric evaluation and item response theory calibration of the PROMIS Pediatric Positive Affect item bank, child-report and parent-proxy editions.
Methods: The initial item pool comprising 53 items, previously developed using qualitative methods, was administered to 1,874 children 8-17 years old and 909 parents of children 5-17 years old. Analyses included descriptive statistics, reliability, factor analysis, differential item functioning, and construct validity. A total of 14 items were deleted, because of poor psychometric performance, and an 8-item short form constructed from the remaining 39 items was administered to a national sample of 1,004 children 8-17 years old, and 1,306 parents of children 5-17 years old. The combined sample was used in item response theory (IRT) calibration analyses.
Results: The final item bank appeared unidimensional, the items appeared locally independent, and the items were free from differential item functioning. The scales showed excellent reliability and convergent and discriminant validity. Positive affect decreased with children's age and was lower for those with a special health care need. After IRT calibration, we found that 4 and 8 item short forms had a high degree of precision (reliability) across a wide range of the latent trait (>4 SD units).
Conclusion: The PROMIS Pediatric Positive Affect item bank and its short forms provide an efficient, precise, and valid assessment of positive affect in children and youth.
Keywords: Item Response Theory; PROMIS; child; experienced well-being; positive affect; subjective well-being.