The stability of intraindividual means and standard deviations of affect

Dynamic characteristics like intraindividual means (iMs) and standard deviations (iSDs) reliably provide insight into the level and variability of emotions people experience within a given window of time. However, it is unclear the extent to which these measures characterize capture stable individual differences rather than transient states and, if so, how many observations are necessary to ensure reliable measurement. In the current study, we use data from two experience sampling studies that use burst designs to test the effect that the number of within-person observations has on the one-week and one-year stability of iMs and iSDs for various measures of emotion. We find that a modest one-year of stability of r = .50 could be reached for iMs with an average of 14 observations per person, while for iSDs an average of 42 observations were necessary, with many items failing to reach r = .50 at the maximum number of observations available. These findings suggest that in typical experience sampling designs iMs capture stable individual differences but iSDs may not, even with many within-person observations.