Psychometric properties of the composite scale of morningness: a shortened version

The Composite Scale of Morningness published in Smith et al. (1989) was translated into Thai and tested on 321 Thai students to assess its cross-cultural applicability. The internal consistency (Cronbachʹs α = 0.79) of the full Thai Composite Scale of Morningness is comparable to that of the English scale. The shortened 7-item scale improves the full scale by deleting items that are redundant or have poor statistical properties. It retains high internal consistency (Cronbachʹs α = 0.70). Two components are extracted from the seven items: ‘Voluntary Schedule’ (items 2, 8, 10 and 11) and ‘Alertness After Waking up/Self-Reported Morningness-Eveningness’ (items 5, 12 and 9). The mean composite scores of morningness do not differ by gender.