Teun Remmers

134 | Chapter 8 Results Participant characteristics In total, 117 boys and 138 girls from 20 primary schools provided valid data. Children were approximately 12 years old. After data-cleaning and applying exclusion criteria, 808 valid days of measurement were retained and 74% of the children provided valid data for at least three days. This resulted in a dataset of around 1.8 million records (i.e. 10-second epochs), which held around 5000 hours of afterschool data collection. Results from an electronic questionnaire that was administered after the measurements (response rate 77% and 75% for the children and parents, respectively), shows that this sample consisted of children from parents with relatively high socio-economic status; 44% of responding parents had at least a higher vocational diploma, and 67.9% of the responding parents had a paid job for at least three days per week. On average, children lived 696.1 meters (SD=735.3) from their school. In total, 92% of the parents reported that their child used active transport to travel to and from school. In addition, 77% reported that their child spent equal or less than 10 minutes per day on afterschool homework (Table 1). Table 1: Characteristics of the study population ( N = 255) n (%) Gender; n boys (missing n = 0) 117 (45.9%) Age; mean years (SD) (missing n = 0) 12.1 (0.5) Valid measurement-days; n ≥ 3 days (missing n = 0) 189 (74.1%) Respondent questionnaire; n mothers (missing n = 54 (21.2%)) 146 (57.3%) Most frequently used transport-mode to school; n bicycling (missing n = 59 (23.1%)) 128 (50.2%) Most frequently used transport-mode to school; n walking (missing n = 59 (23.1%)) 52 (20.4%) Average daily time spent on homework during measurement; n ≤ 10 minutes (missing n = 59 (23.1%)) 150 (58.8%) Educational level of respondent; n secondary vocational or higher education (missing n = 59 (23.1%)) 142 (55.7%) Educational level of respondent's partner; n secondary vocational or higher education (missing n = 59 (23.1%)) 127 (49.8%) Employment of respondent; n ≥ 3 days of paid employment (missing n = 59 (23.1%)) 133 (54.0%) Employment of respondent's partner; n ≥ 3 days of paid employment (missing n = 92 (36.1%)) 151 (59.2%)