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. Author manuscript; available in PMC: 2009 Jul 6.
Published in final edited form as: Alcohol Clin Exp Res. 2008 Mar 4;32(5):723–737. doi: 10.1111/j.1530-0277.2008.00643.x

Table 2.

Mixture Models for Heavy Alcohol Use, for Smoking, and for Marijuana Use

AIC BIC Entropy Vuong-Lo-Mendell-Rubin LRT (p-value)
Heavy drinking (n = 31,939)
  2 classesa 305657.94 305833.74 0.94 <0.001
  3 classes 300408.64 300617.93 0.83 <0.001
  4 classes 289682.53 289925.31 0.90 <0.001
Smoking (n = 31,952)
  2 classes 295847.47 295981.42 0.95 <0.001
  3 classes 283840.21 283999.28 0.99 <0.001
  4 classes 275359.47 275543.65 0.94 <0.001
  5 classes 266864.32 267073.62 0.94 <0.001
  6 classesc 265235.94 265235.94 0.70 0.49
Marijuana use (n = 31,961)
  2 classes 306752.76 306928.58 0.99 <0.001
  3 classes 290694.36 290903.67 0.97 <0.001
  4 classes 275215.38 289160.32 0.97 <0.001
  5 classesb 269909.77 270177.68 0.97 <0.001
  6 classesc 266973.74 267283.52 0.69 0.50

LRT, likelihood ratio test.

a

This model had an improper solution (nonpositive definite residual covariance matrix) that could not be resolved. Although none of the growth factors had negative variances, it appears likely that the model which extracted 2 classes over-estimated the variance in the quadratic factor. However, given that it is an independence model against which to compare solutions with greater than 2 classes, we retain it in the Table for reference.

b

As this model had an improper solution (nonpositive definite residual covariance matrix), the Year 1 residual variance was constrained to zero.

c

This model had an improper solution (nonpositive definite first-order derivative matrix) that could not be resolved.

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