Crystal Smit

Social Network Intervention vs. Mass Media Intervention 4 71 of the children indicated that the goal of the study was for influence agents to promote water consumption. Participants The study was part of the second data collection phase of the MyMovez research program (Bevelander et al., 2018). Participants were recruited through their school. All schools following a regular education program were eligible for participation. As shown in Figure 4.1, 150 urban and suburban schools in the Netherlands were invited to participate in the second phase of the MyMovez research program. Twenty-one schools expressed interest in participating; however, two of these schools were unable to participate due to not receiving enough active consents from caregivers as well as children themselves ( < 60% in each classroom (Marks, Babcock, Cillessen, & Crick, 2013). Of these 19 remaining schools, eight schools were assigned to three other conditions from the MyMovez research program that focused on promoting physical activity (van Woudenberg et al., 2020). The current study consisted of the 11 schools that were randomly assigned to one of the three conditions that focused on children’s drinking behaviors. Five schools were assigned to the social network intervention, three to the active control condition and three to the control condition. These schools were located in different areas in the Netherlands, with considerable geographical distance between the conditions (social network intervention vs. active control schools ranged from 36 to 203 km; social network intervention vs. control schools ranged from 30 to 203 km; active control vs. control schools ranged from 20 km to 197 km). Therefore, the risk of between-group contamination was negligible. Out of the 579 children in these 11 schools, a total of 128 (22%) caretakers did not provide consent for their child to participate. Thus, the sample consisted of 451 children (50.8% girls) between 9 and 14 years old ( M = 10.74 years; SD = .97). Of these children, 149 (47.7% girls) were allocated to the social network intervention, 164 (56.1% girls) to the active control condition and 138 (47.8% girls) to the control condition (see Figure 4.1 for the flow diagram of study participants). The number of participating children was 443 at T1, 442 at T2 and 443 at T3.