Table 1. Summary of the demographic data of participants.
| Sample | N | Male (%) | Age (M ± SD) | N of collection (rate of availability) | Geographic regions |
| Sample 1 | 408 | 52.5 | 21.2±2.0 | 480 (85.0%) | Eastern China |
| Sample 2 | 200 | 38.5 | 22.9±1.7 | 240 (83.3%) | Eastern China |
| Sample 3 | 953 | 36.4 | 22.0±3.0 | 953 (100%) | all of China’s regions except Eastern China |
| Sample 4 | 381 | 75.6 | 18.2±1.5 | 480 (79.4%) | Eastern China |
| Sample 5 | 996 | 76.6 | 18.3±1.8 | 1280 (77.9%) | Eastern China |
| Norm | 1949 | 57.0 | 20.1±3.1 | 2233 (87.3%) | all of China’s regions |
Note. Norm comprises sample 3 and sample 5.