Table 1.
Characteristics of the different national samples
| Germany | Italy | South Africa | Spain | Sweden | |
|---|---|---|---|---|---|
| Data collection | School (pupils) | School (pupils) | School (pupils) | School (pupils) | Postal survey (from general population) |
| Study design | Cross-sectional | Cross-sectional & retest | Cross-sectional | Cross-sectional & retest | Cross-sectional |
| Mode of recruitment | Random sample | Convenience sample | Convenience sample | Convenience sample | Random sample |
| Method of application | Paper–pencil | Paper–pencil | Paper–pencil | Paper–pencil | Paper–pencil |
| N | 756 | 415 | 258 | 973 | 407 |
| Male | 385 | 199 | 130 | 494 | 208 |
| Female | 371 | 216 | 128 | 479 | 199 |
| Age-range | 10–18 | 8–15 | 13–19 | 8–18 | 8–16 |
| Mean age (SD) | 13.8 (1.9) | 11.8 (2.2) | 15.5 (1.3) | 13.0 (2.7) | 13.2 (2.7) |