Table 1 Descriptive statistics of the entire study sample (N = 270)
|  | Mean ± SD | Frequencies (%) | 95% confidence limits |
|---|---|---|---|
Age | 13.42 ± 1.28 |  | 13.27 – 13.57 |
Sex | Â | Â | Â |
Boys | 143 (53.0%) | ||
Girls | 127 | ||
Ethnicity | Â | Â | Â |
Native Dutch | 248 (91.9%) | ||
Non-native Dutch | 22 | ||
Academic year | Â | Â | Â |
Grade 7 | 136 (50.4%) | ||
Grade 9 | 134 | ||
School level | Â | Â | Â |
Senior general secondary education | 73 (27.0%) | ||
University preparatory education | 197 | ||
SES | Â | Â | Â |
Low-medium | 65 (24.4%) | ||
High | 201 | ||
BMI (kg/m 2 ) | 19.14 ± 2.70 |  | 18.81 – 19.46 |
Depressive symptoms | 10.86 ± 8.26 |  | 9.86 – 11.86 |
Total time spent moving per week (min.) | 834.60 ± 215.21 |  | 806.76 – 862.44 |
Active commuting to school (min./week) | 230.80 ± 94.75 |  | 219.44 – 242.15 |
Time spent moving per week corrected for active commuting to school (min.) | 602.90 ± 188.91 |  | 578.46 – 627.33 |
Active commuting to school as % of total time spent moving per week | 28.15 ± 10.34 |  | 26.60 – 30.40 |
D2 Test of attention | 175.84 ± 26.66 |  | 172.61 – 179.06 |
Symbol Digit Modalities Test | 60.11 ± 10.50 |  | 58.83 – 61.40 |
Academic Achievement | 6.83 ± 0.78 |  | 6.73 – 6.92 |
Mathematics performance | 6.97 ± 1.10 |  | 6.84 – 7.10 |