. Author manuscript; available in PMC: 2017 Mar 1.

Published in final edited form as: Sleep Breath. 2016 Jan 25;20(1):293–301. doi: 10.1007/s11325-016-1313-4

Table 2.

Item Characteristics, item-total correlation, alpha if item deleted from the Pittsburgh Sleep Quality Index (PSQI) among pregnant women (N=1,488)

Components	Mean	SD	Corrected item- total correlation	Alpha if item deleted
1. Sleep duration	0.22	0.54	0.57	0.71
2. Sleep disturbance	1.34	0.51	0.44	0.73
3. Sleep latency	0.81	0.79	0.54	0.70
4. Daytime dysfunction due to sleepiness	0.97	0.78	0.39	0.72
5. Sleep efficiency	0.58	0.89	0.62	0.69
6. Subjective sleep quality	1.12	0.67	0.64	0.70
7. Sleep medication use	0.18	0.56	0.31	0.74
Global PSQI score	5.23	2.84

Overall Cronbach’s alpha (the overall reliability of the PSQI) is 0.74

Abbreviations: SD, standard deviation

“Corrected item-total correlation” are the correlations between each components and the global PSQI score.

“Alpha if item deleted” – represents the PSQI’s Cronbach alpha reliability coefficient for internal consistence if the specific item is removed from the scale.