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

Table 4

Intervention effect for all types of vaginal sex episodes outcome from ZIP and ZINB.

Variables	Coefficient of intervention with control as a reference	Standard Error	Chi-square	𝑃 value
Poisson regression part from ZIP
3 months	−0.1495	0.0255	34.44	<0.0001
6 months	−0.1373	0.0252	29.68	<0.0001
12 months	−0.1400	0.0238	34.65	<0.0001
Negative binomial part from ZINB
3 month	−0.2215	0.0795	−2.79	0.0055
6 months	−0.1407	0.0888	−1.58	0.1138
12 months	−0.1911	0.0966	−1.98	0.0486
Logistic regression Part from ZIP
3 months	0.2252	0.2409	0.87	0.3499
6 months	0.7859	0.2407	10.66	0.0011
12 months	0.1227	0.2534	0.23	0.6282
Logistic regression part from ZINB
3 months	−0.2144	0.5684	−1.22	0.2208
6 months	1.0068	0.3521	2.86	0.0044
12 months	0.0813	0.3306	0.25	0.8059