Table 2.

Transitional Probabilities Estimated with PDES Method/1997 NSDUH data (N=8,731) and the Conventional Method and the NLSY97 Data (n=7,286^*).

Age (year)	Sigma1	Sigma 2	Sigma 3	Sigma 4	Sigma 5	Sigma 6	Sigma 7
PDES method and the cross-sectional 1997 NSDUH dataa
13	0.880	0.070	0.050	0.193	0.807	0.476	0.526
14	0.859	0.074	0.068	0.174	0.826	0.437	0.563
15	0.836	0.089	0.076	0.187	0.814	0.400	0.600
16	0.863	0.066	0.071	0.196	0.804	0.430	0.570
17	0.891	0.045	0.046	0.148	0.853	0.442	0.558
Directly estimated with the 1997 National Longitudinal Survey datab
13	0.885	0.067	0.048	0.159	0.841	0.425	0.575
14	0.889	0.059	0.052	0.115	0.885	0.409	0.591
15	0.889	0.065	0.046	0.068	0.932	0.387	0.613
16	0.873	0.083	0.044	0.088	0.912	0.426	0.574
17	0.884	0.073	0.043	0.080	0.920	0.423	0.577
Differences between the two estimations (13-17 years old)
Mean	0.002	0.020	0.076	0.076	0.020	0.020	0.016
SD	0.023	0.012	0.038	0.038	0.016	0.016	0.024
P (t test)	>0.05	>0.05	>0.05	>0.05	>0.05	>0.05	>0.05

^aNote: Transitional probabilities were estimated with one-year cross-sectional data from the 1997 National Survey on Drug Use and Health.

^bTransitional probabilities were estimated with data collected among youth who participated the baseline and the follow-up survey from the National Longitudinal Survey of Youth 1997. See Figure 1 and the corresponding text for definitions of the seven transitional probabilities.

^*This sample contained only participants who provided completed data at both baseline survey in 1997 and follow-up survey in 1998.