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. Author manuscript; available in PMC: 2013 Jul 1.
Published in final edited form as: J Adolesc Health. 2012 Feb 23;51(1):45–52. doi: 10.1016/j.jadohealth.2011.11.008

Table 3.

Mediated effects of contextual variables through individual variables on aggression trajectories.

Mediator Indirect Effect (ab) z SE Percent Mediated
African Americans
Parental involvement Alcohol use 0.255 1.60 0.16 9.7
Marijuana use 0.176 1.19 0.15 6.7
Unsupervised time 0.138 5.80*** 0.02 5.2
Depression 0.183 5.06*** 0.04 6.9
Academic achievement 0.139 4.61*** 0.03 5.3
Group fighting 0.416 3.65*** 0.11 15.7
Baseline aggression 0.414 6.05*** 0.07 15.7
Total 65.2
Adults in neighborhood use alcohol Alcohol use 0.398 1.55 0.26 18.2
Marijuana use 0.195 1.19 0.16 8.9
Unsupervised time 0.109 5.03*** 0.02 4.9
Depression 0.141 4.49*** 0.03 6.4
Academic achievement 0.101 4.17*** 0.02 4.6
Group fighting 0.345 3.58*** 0.09 15.8
Baseline aggression 0.347 4.32*** 0.08 15.9
Total 74.9
Peer alcohol use Alcohol use 0.283 1.39 0.20 12.1
Marijuana use 0.146 0.94 0.15 6.3
Unsupervised time 0.088 4.41*** 0.02 3.7
Depression 0.118 4.14*** 0.03 5.1
Academic achievement 0.079 4.13*** 0.02 3.4
Group fighting 0.411 3.31*** 0.12 17.6
Baseline aggression 0.492 3.18** 0.15 21.1
Total 69.4
Hispanics
Parental involvement Alcohol use 0.337 1.69 0.20 12.5
Marijuana use1
Unsupervised time 0.153 6.31*** 0.02 5.6
Depression 0.187 6.48*** 0.03 6.9
Academic achievement 0.239 5.94*** 0.04 8.9
Acculturation 0.059 4.95*** 0.01 2.2
Group fighting 0.274 3.96*** 0.07 10.1
Baseline aggression 0.053 6.80*** 0.08 19.8
Total 65.9
Adults in neighborhood use alcohol Alcohol use 0.219 2.39* 0.09 11.9
Marijuana use1
Unsupervised time 0.143 5.03*** 0.03 7.8
Depression 0.070 2.76** 0.03 3.8
Academic achievement 0.191 5.00*** 0.04 10.3
Acculturation 0.026 4.51*** 0.006 1.5
Group fighting 0.209 3.68*** 0.06 11.4
Baseline aggression 0.458 5.22*** 0.09 24.9
Total 71.7
Home access to alcohol Alcohol use 0.311 2.32* 0.13 16.7
Marijuana use1
Unsupervised time 0.140 5.02*** 0.03 7.6
Depression 0.123 4.29*** 0.03 6.6
Academic achievement 0.217 5.05*** 0.04 11.7
Acculturation 0.030 4.06*** 0.007 1.6
Group fighting 0.227 3.50*** 0.06 12.2
Baseline aggression 0.397 4.84*** 0.08 21.4
Total 77.9
Peer alcohol use Alcohol use 0.209 2.12* 0.09 9.8
Marijuana use1
Unsupervised time 0.099 4.57*** 0.02 4.6
Depression 0.160 5.03*** 0.03 7.5
Academic achievement 0.187 4.49*** 0.04 8.8
Acculturation 0.021 4.24*** 0.005 0.9
Group fighting 0.266 3.45*** 0.08 12.5
Baseline aggression 0.479 4.57*** 0.10 22.5
Total 66.7

Notes: All models are adjusted for demographics and treatment. Clustered robust standard errors were calculated to account for the clustered sampling design.

(a)

These mediated effects were generated in accordance with MacKinnon34 and Komro, Perry, Williams, Stigler, Farbakhsh, & Veblen-Mortenson.35 The percent mediation was generated using the formula: [(a*b/(a*b + c)] 34.

(b)

Indirect effects are not directly comparable across variables. Percent mediation is comparable across variables and groups of variables.

1

Because marijuana use was perfectly correlated with aggression (no Hispanics who were aggressive reported using marijuana), a mediated effect could not be estimated.

**

p<0.01

***

p<0.001