Data management and statistical analysis
REGRESSION, REGRESSION
Data from the questionnaire was entered into a database by two research assistants blinded to the assignment of the participants. Participants’ characteristics were examined and summarized within all participants and with respect to intervention and control groups. A comparison of the distributions was performed using an unpaired t-test for each continuous variable or a Chi-squared test for each binary or categorical variable. The P-values and the descriptive statistics including the mean ± standard deviation (SD) for continuous variables or the number and percentage of participants out of the total number of participants [n (%)] for binary and categorical variables were presented.The distribution of total scores, as well as scores from understanding and behavior domains of the questionnaire, were examined both within-participants and between intervention and control groups. The differences in the scores from before to immediate or 1-month after the intervention within each participant were examined using paired t-test. Changes in scores within each participant from before to immediate or 1-month after the intervention were obtained by subtracting the baseline scores from the later scores, respectively. The changes in questionnaire scores (outcomes) within each group were examined using t-test comparisons. Regression analyses using generalized estimating equations (GEE) were also performed to examine the changes in outcomes with a repeated measure design and adjustment for covariates including age (interval), sex (binary), race (nominal), ethnicity (binary), income level (ordinal), and assigned classrooms (nominal) as appropriate. Given that only few students provided race classification (22 out of 77) and the skewed distribution of family income levels of participants, only age, sex, and ethnicity were included in the final regression modeling. Furthermore, linear regression modeling with adjustment for covariates was performed for comparison of changes between the intervention and the control group at different time points.Data management and statistical analyses were conducted in Stata/IC (version 14.2, Stata Corp LP, College Station, TX, USA) and R software (version 4.2.2; R Foundation for Statistical Computing, Vienna, Austria). Figures were generated in GraphPad software (Prism version 7.0, San Diego, CA, USA). A significance level of α<0.05 was used to determine statistical significance.