Table 3. Number of items, number of losses, estimates of Cronbach’s alpha and of stratified Cronbach’s alpha of the SQR-20 dimensions extracted by tetrachoric factor analysis among groups of workers. Bahia, Northeastern Brazil, 2006-2013.

Study - Population (N)	Items (N)	Losses	Cronbach’s alpha	Cronbach’s alpha (Tetrachoric)
Study 1 – Informal workers (N = 1,453)
F1 - Depressive mood/Anxiety symptoms	11	5	0.79	0.90
F2 - Somatic component	5	0	0.65	0.79
F3 - Decreased energy	4	0	0.65	0.76
Scale total	20	5	0.85	0.92
Stratified Cronbach’s alpha	-	-	0.86	0.93
Study 2 – Teachers (N = 3,891)
F1 - Decreased energy/Anxiety symptoms	11	434	0.82	0.92
F2 - Somatic component	6	295	0.68	0.82
F3 - Depressive mood	3	242	0.41	0.74
Scale total	20	605	0.85	0.93
Stratified Cronbach’s alpha	-	-	0.82	0.94
Study 3 – Health care workers (N = 2,397)
F1 - Depressive mood	9	33	0.67	0.87
F2 - Decreased energy/Anxiety symptoms	9	44	0.72	0.87
F3 - Somatic component	2	17	0.70	0.87
Scale total	20	60	0.82	0.92
Stratified Cronbach’s alpha	-	-	0.83	0.93
Study 4 – Urban workers (N = 1,539)
F1 - Somatic component/Anxiety symptoms	11	8	0.78	0.88
F2 - Decreased energy	5	6	0.62	0.82
F3 - Depressive mood	4	4	0.64	0.86
Scale total	20	18	0.84	0.93
Stratified Cronbach’s alpha	-	-	0.85	0.93