Table 4.

Conditional probabilities for four class model of substance use

Class prevalence	Frequent poly-substance users 6.5 %	Moderate poly-substance users 9.1 %	Alcohol experimenters 25.8 %	Non-users 58.5 %
Smoke
Never used	0.107	0.200	0.502	0.953
No recent use	0.239	0.456	0.476	0.042
1 or 2 days recent use	0.155	0.275	0.017	0.004
3 to 9 days recent use	0.182	0.063	0.003	0.000
10 to 30 days recent use	0.317	0.006	0.003	0.001
Alcohol
Never used	0.028	0.026	0.178	0.867
No recent use	0.084	0.124	0.525	0.081
1 or 2 days recent use	0.159	0.503	0.221	0.041
3 to 9 days recent use	0.361	0.308	0.051	0.006
10 to 30 days recent use	0.368	0.039	0.025	0.004
Marijuana
Never used	0.083	0.266	0.635	0.994
No recent use	0.180	0.300	0.304	0.002
1 or 2 days recent use	0.133	0.268	0.036	0.002
3 to 9 days recent use	0.178	0.131	0.014	0.001
10 to 30 days recent use	0.426	0.034	0.012	0.001