Table 2. Cronbach’s alpha (KD-20) and tetrachoric correlation matrix alpha values of the items composing SRQ-20, according to group of workers. Bahia, Northeastern Brazil, 2006-2013.

	Group of workers
	Informal workers		Teachers		Health care workers		Urban workers
	(n = 1,453)a		(n = 3,891)b		(n = 2,397)c		(n = 1,539)d
SRQ-20 items	α1e	α2f	α1e	α2f	α1e	α2f	α1e	α2f
1. Do you often have headaches?	0.85	0.93	0.85	0.93	0.82	0.92	0.84	0.92
2. Is your appetite poor?	0.84	0.93	0.85	0.93	0.82	0.92	0.83	0.92
3. Do you sleep badly?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
4. Are you easily frightened?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
5. Do your hands shake?	0.84	0.93	0.85	0.93	0.81	0.91	0.84	0.92
6. Do you feel nervous, tense or worried?	0.84	0.93	0.84	0.93	0.80	0.91	0.83	0.92
7. Is your digestion poor?	0.84	0.92	0.85	0.93	0.81	0.91	0.84	0.92
8. Do you have trouble thinking clearly?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
9. Do you feel unhappy?	0.84	0.92	0.84	0.93	0.80	0.90	0.83	0.92
10. Do you cry more than usual?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
11. Do you find it difficult to enjoy your daily activities?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
12. Do you find it difficult to make decisions?	0.84	0.93	0.85	0.93	0.81	0.91	0.84	0.92
13. Is your daily work suffering?	0.84	0.93	0.85	0.93	0.82	0.91	0.84	0.92
14. Are you unable to play a useful part in life?	0.85	0.93	0.86	0.94	0.82	0.92	0.83	0.92
15. Have you lost interest in things?	0.84	0.92	0.85	0.93	0.81	0.91	0.83	0.92
16. Do you feel that you are a worthless person?	0.85	0.93	0.86	0.93	0.82	0.92	0.84	0.92
17. Has the thought of ending your life been on your mind?	0.85	0.93	0.86	0.94	0.82	0.91	0.84	0.92
18. Do you feel tired all the time?	0.84	0.93	0.84	0.93	0.81	0.91	0.83	0.92
19. Do you have uncomfortable feelings in your stomach?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
20. Are you easily tired?	0.84	0.93	0.85	0.93	0.81	0.91	0.83	0.92
Total	0.85	0.94	0.85	0.94	0.82	0.92	0.84	0.93

^a 0.3% losses.

^b 13.5% losses.

^c 2.4% losses.

^d 1.2% losses.

^e Cronbach’s alpha (KD-20), if the item is removed.

^f Cronbach’s alpha for the tetrachoric correlation matrix, if the item is removed.