A Preliminary Study on the Korean Translation of Composite Scale(KtCS) to Measure Morningness: Eveningness

Yoon, Jin Sang; Shin, Sang Mun; Kook, Seung Hee; Lee, Hyung Yung

Abstract

OBJECT: The Composite Scale by Smith et al. has been proposed as an improved measure of momingness-eveningness. This study attempted to endorse that a Korean translation of Composite Scale(KtCS) can be useful to differentiate people according to circadianrhythm types. METHOD: KtCS and Life Habit Questionnaire(LHQ) were administered to 561 university students. LHQ consisted of items questioning sleep habits on weekdays(bedtime, rising time and sleep length), the time of perceived peak alertness(mental and physical), time of perceived peak performance(mental, physical and academic), and quality of academic performance during the morning, afternoon and evening. Subjects were categorized on the basis of their KtCS scores into evening(I) types, intermediate(I) types, and morning(M) types. The cut-off points for these categories were set at the 10th and 90th percentiles. In addition 7 I-type and 7 M-type subjects were selected from the student population who had participated in the previous survey and then, oral temperature of each subject was taken every hour torn 08 : 00 to 22 : 00. To assess both the internal and the external measurement properties of KtCS, descriptive statistics, reliability and validity were examined.
RESULTS
The distribution of KtCS scores was significantly, negatively skewed. The KtCS scores closest to the 10th and 90th percentiles were 26 and 41 respectively. The split-half reliability(. 85), test-retest reliability( .91), and internal consistency(Cronbach alpha, .82) were obtained above the expected. Inter-item correlations were all positive and ranged from .10-.59 with a mean of .25. Item-total correlations varied from .33 to .63 with a mean of .45. Common factor analyses confirmed three factors: preferred times of performance and going to bed, arising time, and morning alertness. The validity of KtCS was further demonstrated through strong relationships between the scale and external criteria.4 discernable difference in oral temperature between the M-type and the type across morning to evening provided additional evidence for validity of the scale.
CONCLUSIONS
The results would suggest the possibility that KtCS can be employed as a tool for selection of I-type people or M-type people. It is as yet, however, uncertain that KtCS might be suitable to select people for night shiftwork because the subjects of this study are limited to university students. Therefore, future research among varying types of people are required to endorse this study.