Psychometric properties of the Diurnal Type Scale of Torsvall and Åkerstedt (1980)

The psychometric properties of the Diurnal Type Scale (DTS) of Torsvall and Åkerstedt (1980) when used on a young sample with no or limited experience of shiftwork were investigated. Four hundred and forty-five students completed the DTS, the Morningness-Eveningness Questionnaire (MEQ) (Home and Östberg 1976), and the Circadian Type Questionnaire (CTQ) (Folkard et al. 1979). The DTS was not found to be a homogeneous scale (Cronbach's alpha = 0·29) and appeared to be assessing two relatively independent dimensions: morningness and eveningness. Adequate test-retest reliability was found when subjects remained as students (r = 0·78), however, scores obtained from students did not correlate highly (r = 0·43) with those obtained when they were working on rotating shifts. The DTS correlated only moderately with the MEQ (r = 0·50) and with the CTQ. Future researchers should be cautious in using the instrument until they have information about its psychometric properties when applied to their population of interest.