Table 2. Results of logistic regression for the association of body louse infestation with certain explanatory variables in a homeless population surveyed during 2008–2010 and 2012, San Francisco, California, USA .

Coefficient	Estimated values	SE	p value	Odds ratio	95% CI
Intercept	−3.82	0.73	<0.01	Reference*	–
Sleeping outdoors	0.98	0.37	0.01	2.66	1.29–5.59
African American†	1.03	0.40	0.01	2.81	1.30–6.23
Male	1.73	0.52	0.00	5.64	2.19–17.57
Reason for requesting services, lice‡	1.22	0.60	0.04	3.39	1.09–1.21

*Reference group is female, who sleep indoors, of ethnic self-reported background other than African American, and who requested services for reasons other than body lice.
†All other races/ethnicities combined (white, Hispanic, native American, and Asian) was used as the reference group for this variable on the basis of the results of the univariate analysis
‡All other reasons for requesting services (bugs, itch, and services, such as t-shirts) was used as the reference group for this variable on the basis of the results of the univariate analysis