Esther Mertens

| 27 Study Protocol effectiveness of R&W. Although, this positive effect of involvement of multiple systems is not always found (e.g., Durlak, Weissberg, Dymnicki, Taylor, & Schellinger, 2011). We will examine if R&W is more effective the more parties are involved, as suggested by Durlak and colleagues (2011). We hypothesize that students’ improvements will be more evident the more parties are involved. The second aim is to examine potential moderators of the effect of R&W. Several student characteristics will be examined as moderators: Gender, ethnicity, and personality. In the R&W program the emphasis is on physical exercises which might lead to differential effectiveness based on gender and ethnicity. There are differences in the levels of daily physical activity between boys and girls with girls being less physically active (e.g., Minges, Chao, nam, Grey, & Whittemore, 2015; Patnode et al., 2010). Girls appear to experience higher barriers for physical activities than boys. They are more afraid of being chosen last for a team and of being embarrassed (Patnode et al., 2010). Therefore, we hypothesize that R&W is more effective for boys. Also between ethnicities there are differences in the amount and sort of physical activities adolescents engage in. For instance, Black and Asian adolescents are less physically active and showmore sedentary behavior than White adolescents (Minges et al., 2015, Brodersen, Steptoe, Boniface, & Wardle, 2007). White girls are more likely to be active in sports teams than Hispanic girls whom are more likely to be active in walking for transportation or physical activities at home such as household chores (Kelly et al., 2010). Kelly and colleagues (2010) suggest to tailor physical activity programs based on ethnicity due to differences in factors related to physical activation. For example, White girls appear to have higher levels of self-efficacy related to physical activities which makes them more physically active than Black and Hispanic girls. It might be that White students are more familiar with the sort of physical exercises used in the R&W program than students with other ethnicities. These White students might be less out of their comfort zone due to which they can focus more on the other aspects of the intervention. Thus, we hypothesize that R&W is more effective for White students than for students with other ethnicities. Previous intervention research has shown that personality can be a moderator of intervention effectiveness. Senf and Liau (2013) have found the strongest intervention effects on happiness for individuals with high levels of extraversion and openness and on depressive symptoms for individuals with high levels of extraversion. Asscher and colleagues (2016) have shown that Multisystemic Therapy was less effective than treatment as usual in decreasing rule-breaking behavior for adolescent with low levels of agreeableness. Stoltz and colleagues (2013) have found the strongest intervention effects on reactive aggression for children with a low level of extraversion and on proactive aggression for children with less extreme levels of conscientiousness. Hence, it is expected that personality also influences the effectiveness of R&W. It is hypothesized that R&W is most effective for students with higher levels of agreeableness and openness, and average levels of conscientiousness. No specific hypothesis concerning extraversion is stated, since the results (Senf & Liau, 2013; Stoltz et al., 2013) are inconsistent. 2