More than counting: An intraindividual variability approach to categorical repeated measures

Objectives: Age-related differences in daily experiences are often described using summaries of categorical repeated measures, including typologies of stressors, activities, social partners, and coping strategies. This paper illustrates how an intraindividual variability (IIV) framework can be used to extract additional meaning from categorical IIV data. Method: Using 8-occasion categorical data on daily stressors from the National Study of Daily Experiences (N = 1,499, M_Age = 46.74, SD_Age = 12.91), we derive and compute six IIV metrics that invoke numeric and nominal measurement of the central tendency, dispersion, and asymmetry of individuals' stressor experiences and examine how these metrics, relative dominance, diversity, log-skew and mode, spread, order, are related to age and interindividual differences in negative affect. Results: Results demonstrate the utility of the numeric and nominal categorical IIV metrics, with theoretically meaningful age gradients in the three numeric IIV stressor metrics and five of six IIV metrics mapping differences in negative affect. Discussion: Findings highlight how the unique constructs measured by these six metrics of categorical IIV may be used to examine dynamic process, study interindividual and age-related differences, and expand the variety of developmental research questions that may be answered using categorical repeated measures data.