Patient-reported outcomes to assess the efficacy of extended-release guaifenesin for the treatment of acute respiratory tract infection symptoms

Table 6 Internal consistency reliability symptom subscale (items 1, 2, 4, 5, 8, 9, 10 and 11) score at Days 1, 4, and 8 (Cronbach’s Alpha)

Item	Cronbach’s alpha			Cronbach’s alpha with item deleted
	Day 1	Day 4	Day 8	Day 1	Day 4	Day 8
Subscale score alpha	0.76	0.87	0.90
	(n = 310)	(n = 305)	(n = 290)
1. Bring up phlegm				0.73	0.84	0.88
2. Difficult to breathe				0.72	0.84	0.88
4. Annoyed by phlegm				0.71	0.83	0.87
5. Interference with ability to speak				0.71	0.84	0.88
8. Phlegm thickness				0.72	0.85	0.88
9. Difficulty bringing up phlegm				0.81	0.90	0.93
10. Cough when woke up				0.73	0.84	0.88
11. Cough during day				0.74	0.84	0.88

ISSN: 1465-993X