The Measurement of Subjective Wellbeing: Item-Order Effects in the Personal Wellbeing Index—Adult

When multi-item questionnaires are included in psychological research, many factors can influence the response given. One such factor that has traditionally been overlooked is the potential impact of item-order effects. This paper extends upon the work of Kaplan et al. (J Happiness Stud 14:1443–1458, 2013. doi: 10.​1007/​s10902-012-9388-5) who explored item-order effects in measures of job satisfaction, and applies similar principles to the measurement of life satisfaction, or subjective wellbeing, by exploring item-order effects within the Personal Wellbeing Index (PWI; IWBG in Personal Wellbeing Index, 5th edn. Australian Centre on Quality of Life, Deakin University, Melbourne, 2013. http://​www.​deakin.​edu.​au/​research/​acqol/​intruments/​wellbeing-index/​index.​php). In a preliminary study, participants completed the PWI in its standard format (general-specific) and psychometric properties were compared to those who completed the PWI in an alternate format (specific-general). Analyses revealed that the PWI performed adequately for both groups, though there were subtle indications of item-order effects. In a second study, the order of the PWI domains was randomised (random-order) and compared to the standard format (fixed-order). Results revealed lower mean scores and more variation in scores when items were randomised. Overall, the PWI performed as expected for most interrogative analyses. It achieved a single factor solution, no matter the order of items, and the same domains emerged as significant unique predictors of general life satisfaction. The study highlights the importance of exploring item-order effects as part of the psychometric validation procedure, and it is recommended that all new scales be subject to this investigation to reduce measurement error and improve accuracy in psychological assessment.