Chapter 12: Modeling Variation in Intensive Longitudinal Data

Modern data collection procedures, such as ecological momentary assessments (EMA) (Shiffman et al., 2008; Smyth & Stone, 2003; Stone & Shiftman, 1994), experience sampling (de Vries, 1992; Feldman Barrett & Barrett, 2001; Scollon et al., 2003), and diary methods (Bolger et al., 2003), have been developed to record the momentary events and experiences of subjects in daily life. These procedures yield relatively large numbers of subjects and observations per subject, and data from these designs are sometimes referred to as intensive longitudinal data (Walls & Schafer, 2006). Such designs follow the “bursts of measurement” approach described by Nesselroade and McCollam (2000), who called for such an approach in order to assess intra-individual variability. In this approach, a large number of measurements are obtained over a relatively short time span (e.g., a week). As noted by Nesselroade and McCollam (2000), this increases the research burden in several ways; however, it is important for studying intra-individual variation and to explain why subjects differ in variability rather than solely in mean level (Bolger et al., 2003). In this chapter, we describe data from an EMA study of adolescents, where interest was on determinants of the variation in the adolescents’ moods.