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The Effects of Sanction Intensity on Criminal Conduct - JDAI Helpdesk

The Effects of Sanction Intensity on Criminal Conduct - JDAI Helpdesk

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treatment group, and those to the right favor the c<strong>on</strong>trol group. When the c<strong>on</strong>fidence<br />

intervals do not touch or cross the center line, the point estimate is statistically<br />

significant.<br />

We assume a random effects model, rather than fixed effects, for all analyses (see<br />

Appendix C for details). Fixed effects models in meta-analysis assume that the <strong>on</strong>ly<br />

random error in the distributi<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> effect sizes arises from within-study sampling error.<br />

We do not c<strong>on</strong>sider this to be theoretically justified in our analysis because <str<strong>on</strong>g>of</str<strong>on</strong>g> the<br />

c<strong>on</strong>siderable between-study differences (heterogeneity: see below) in program<br />

characteristics, settings, and populati<strong>on</strong>s. Further, because we know we have not been<br />

able to capture all the available research <strong>on</strong> intensive probati<strong>on</strong> programs, we can<br />

c<strong>on</strong>sider our set <str<strong>on</strong>g>of</str<strong>on</strong>g> studies a sub-sample <str<strong>on</strong>g>of</str<strong>on</strong>g> a larger ‘populati<strong>on</strong>’ <str<strong>on</strong>g>of</str<strong>on</strong>g> studies, with its own<br />

sampling error. Both <str<strong>on</strong>g>of</str<strong>on</strong>g> these factors justify the use <str<strong>on</strong>g>of</str<strong>on</strong>g> the random effects model (Lipsey<br />

& Wils<strong>on</strong>, 2001, pp. 117-120). 10<br />

Meta-analytic methods are also used to investigate whether the overall mean<br />

effect size is moderated by other factors. We are interested in the potential impact <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

certain program and <str<strong>on</strong>g>of</str<strong>on</strong>g>fender characteristics <strong>on</strong> the variati<strong>on</strong> in effect sizes across studies.<br />

Because all our moderator variables are categorical and we have a small set <str<strong>on</strong>g>of</str<strong>on</strong>g> a priori<br />

hypotheses about potential moderators, such as risk/need level and supervisi<strong>on</strong><br />

philosophy, we use the meta-analytic analog to the analysis <str<strong>on</strong>g>of</str<strong>on</strong>g> variance (ANOVA) to test<br />

whether these factors might account for any variability in the observed effect sizes from<br />

each study (Lipsey & Wils<strong>on</strong>, 2001, pp. 120-122). We assess each categorical variable<br />

separately using this strategy. Even though we include a substantial number <str<strong>on</strong>g>of</str<strong>on</strong>g> studies in<br />

this meta-analysis, cell frequencies became very small when they were broken out by<br />

22

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