TABLE 3—

Parameter Estimates (B) for Covariate Effects in Discrete-Time Hazard Models of Age of First Marijuana Use

	Regression Estimates
	Ba (SE)	Odds Ratio
Sample
NP tribes	–.26* (–.11)	.78
SW tribe	–.90* (–.12)	.41
Birth cohort × sample
Younger, NP tribes	.56* (–.11)	1.75
Younger, SW tribe	.74* (–.12)	2.09
Male gender	.54* (–.07)	1.72
Birth cohort × gender
Younger males	–.37* (–.08)	.69
Sample × gender
Males, NP tribes	.01 (–.10)	1.01
Males, SW tribe	.39* (–.12)	1.47

Note. NP = Nothern Plains; SW = Southwest. n = 9492; number of events = 4468.

^aMain effects Bs are the parameter estimates for the referent group, and interaction effects represent differential effects across birth cohorts, genders, and tribes. The SE corresponding to each parameter estimate (B) is the standard error of the estimate.

* P < .001