Table 1. Crude association of sociodemographic variables with sexual initiation in adolescent school students, Piauí, Brazil, 2015.

Variables	Total		Already had sexual intercourse? Yes		PRa	95%CIb	p-valuec
	n	%	n	%
Sex (n = 3,872)
Male	1,820	47.0	623	37.1	2.42	2.04;2.65	< 0.001
Female	2,052	53.0	307	15.6	1.00
Age group (in years) (n = 3,872)d
13 and 14	2,577	66.6	396	15.4	1.00		< 0.001
15 or over	1,295	33.4	540	41.7	2.76	2.33;2.98
Race/skin color (n = 3,867)
White	949	24.6	212	23.8	1.00		0.242
Black	503	13.0	154	31.8	1.38	0.98;1.57
Asian	133	3.4	32	26.9	1.07	0.76;1.52
Mixed race	2,184	56.5	507	24.8	1.04	0.90;1.23
Indigenous	98	2.5	24	29.7	1.11	0.73;1.65
Living with mother (n = 3,869)
Yes	3,417	88.3	771	24.0	0.65	0.54;0.72	< 0.001
No	452	11.7	158	38.5	1.00
Living with father (n = 3,865)
Yes	2,431	62.9	524	21.6	0.75	0.62;0.94	0.035
No	1,434	37.1	403	28.1	1.00
Maternal schooling (n = 2,940)
No schooling	279	9.5	82	30.9	1.52	1.20;1.96	0.001
Elementary education	1,138	38.7	317	28.2	1.42	1.27;1.70
High school education	876	29.8	189	22.0	1.10	0.91;1.39
Higher education	647	22.0	127	22.0	1.00
Type of municipality (n = 3,872)
Capital	2,008	51.9	424	21.8	0.78	0.59;1.15	0.284
Non-capital	1,864	48.1	506	27.0	1.00
Type of school (n = 3,872)
Public	3,077	79.5	801	27.3	1.62	1.53;1.90	< 0.001
Private	795	20.5	129	14.2	1.00
Internet access (n = 3,863)
Yes	2,448	63.4	585	25.6	0.98	0.82;1.12	0.916
No	1,415	36.6	345	25.8	1.00
Number of people in household (n = 3,869)
Living alone	7	0.2	3	23.1	1.41	0.89;2.16	0.493
2-5	2,974	76.9	711	25.6	1.00
6-9	844	21.8	200	24.9	0.99	0.85;1.15
10 or more	44	1.1	15	36.4	1.78	0.76;4.34
Working (n = 3,866)
Yes	305	7.9	148	47.6	2.21	1.90;2.56	< 0.001
No	3,561	92.1	782	23.6	1.00

a) PR: Crude prevalence ratio; b) 95%CI: 95% confidence interval; c) P-value: Chi-square test; d) Sexual initiation n = 3.836.