3.5. Data Analysis
REGRESSION
For comparison analysis between the experimental group and a control group, Chi-square tests were employed to examine if there were significant differences in demographic characteristics, substance use, and risk and protective factors between the two groups. We also used covariance techniques to analyze and assess differences in risk and protective factors for substance use between the experimental and control group at 2- and 3-month follow-up, controlling for baseline measures. ANCOVA was performed to compare the experimental and control groups’ performance on each outcome at baseline and three months. In addition, ANCOVA was used to produce adjusted means, which represent the means of each group once the covariate(s) has been controlled. Logistic regression was used to examine dichotomous dependent variables. The number needed to treat (NNT) and absolute risk reduction (ARR) was also computed. To take into account multiple comparisons, we applied the Bonferroni adjustment.