Affective structure, measurement invariance, and reliability across different experience sampling protocols

While affect is frequently measured with experience sampling methodology (ESM), the affective structure at the between- and within-person level has not been thoroughly investigated. We investigated the affective structure at the between- and within-person level, its invariance across different ESM protocols, and its reliability. Participants (N = 147) were randomly assigned to receive either a 30 or 60 item questionnaire three, six, or nine times per day, resulting in 72–75 participants per questionnaire length and 48–50 participants per sampling frequency. Momentary affect was assessed with 8 or 18 items. At both levels, a structure with two correlated factors showed the best fit compared to an orthogonal and a unidimensional model. A structure with additional freed residual correlations was invariant across protocols at the within-person level and showed high reliability. We observed indications of a more discrete affective structure within than between persons.