Examination of the Dimensionality of Fatigue: The Construction of the Fatigue Assessment Scale (FAS

Summary: This paper reports on two studies. The goal of Study I was to examine the dimensionality of existing fatigue scales. The aims of Study II were to construct a new self-report fatigue instrument and to examine its psychometric qualities. In Study I, 876 respondents completed the Fatigue Scale (Chalder et al., 1993), the Checklist Individual Strength (Vercoulen, Alberts, & Bleijenberg, 1999), the Emotional Exhaustion subscale of the MBI-NL (Schaufeli & Van Dierendonck, 1994), and the Energy and Fatigue subscale of the WHOQOL-100 (De Vries & Van Heck, 1995). Exploratory factor analyses and Mokken Scale Analyses provided strong support for the unidimensionality of each of these fatigue questionnaires. Furthermore, when all four measures were combined, only one factor was found, providing support for the view that fatigue is unidimensional. Based on these analyses, a new measure, the 10-item Fatigue Assessment Scale (FAS), was constructed in Study II. The instrument was administered to a sample of 1893 participants, representative of the Dutch population. The FAS showed a good reliability and content validity. Strong support was obtained for the unidimensionality of the scale