Modeling Count Outcomes from HIV Risk Reduction Interventions: A Comparison of Competing Statistical Models for Count Responses

Table 3

Percentage of zeros captured by the POIS, NB, ZIP, and ZINB models.

Outcome	Observed	POIS	NB	ZIP	ZINB
All types of vaginal sex episodes
3 months	16.353	0.0437	10.968	16.353	11.932
6 months	17.897	0.0417	13.134	16.974	17.877
12 months	16.284	0.0021	11.578	15.449	11.578
Unprotected vaginal sex with steady partners
3 months	43.667	3.836	41.545	43.663	41.545
6 months	42.379	1.664	40.358	42.379	40.358
12 months	33.689	0.298	32.337	33.688	32.337
Unprotected vaginal sex with other partners
3 month	87.608	73.448	87.608	87.516	87.743
6 months	89.610	77.570	89.533	89.565	89.468
12 months	86.498	69.631	86.344	86.481	86.311
Any unprotected vaginal sex with steady or other partners
3 months	39.474	3.322	36.825	39.469	38.617
6 months	39.668	1.753	37.016	39.666	37.016
12 months	29.436	0.225	28.576	29.436	29.597