Abstract
The primary purpose of this exploratory study was to examine the stability and lability of negative mood from a health perspective. Negative mood factor structure was examined in order to evaluate intra-individual change. Few studies have addressed factorial invariance across individuals and across time. The sample was comprised of four women in their 60s and four women in their 80s. Short-term intra-individual change and inter-individual differences in negative mood were assessed with a replicated single-subject design. Participants completed items from the 8SQ questionnaire for 100 consecutive days. P-technique factor analysis was used to examine the structure of negative mood factors, which were than graphed to determine level change over time. The number of factors were consistent, however, the items comprising the factors were not consistent across all participants. Patterns of intra-individual change in the negative mood factor of "fatigue" was found to be highly individualised.