Assessing psychometric properties and measurement invariance of the Sleep Quality Questionnaire among healthcare students

Table 5 Internal consistency and test–retest reliability of the SQQ (N = 595)

	Ordinal Cronbach’s alpha		Ordinal McDonald’s omega		ICC (95% CI)	SEM
	Baseline	Follow-up	Baseline	Follow-up	ICC (95% CI)	Baseline	Follow-up
SQQ	0.823 (0.802, 0.845)	0.851 (0.833, 0.869)	0.822 (0.801, 0.843)	0.852 (0.834, 0.870)	0.816 (0.787, 0.841)	2.617	2.614
SQQ-9	0.845 (0.826, 0.865)	0.876 (0.860, 0.891)	0.849 (0.830, 0.867)	0.879 (0.864, 0.894)	0.802 (0.771, 0.829)	2.425	2.420
SDS	0.710 (0.669, 0.750)	0.733 (0.695, 0.770)	0.731 (0.695, 0.767)	0.749 (0.716, 0.783)	0.741 (0.698, 0.778)	1.236	1.181
DSS (item 2 excluded)	0.798 (0.773, 0.823)	0.831 (0.810, 0.851)	0.794 (0.769, 0.818)	0.831 (0.811, 0.851)	0.815 (0.786, 0.840)	1.895	1.890
DSS	0.860 (0.843, 0.877)	0.885 (0.871, 0.899)	0.862 (0.845, 0.879)	0.888 (0.874, 0.902)	0.829 (0.802, 0.852)	2.099	2.092

SQQ Sleep Quality Questionnaire, SQQ-9 item 2 excluded from the SQQ, SDS Sleep Difficulty Subscale, DSS Daytime Sleepiness Subscale, ICC intraclass correlation coefficient, CI confidence interval, SEM standard error of measurement, calculated as “SD × sqrt (1-ICC)”

ISSN: 2050-7283