Table 2.
Sampling strategy for the study population.
| Study site | Number of selected districts | Names of selected districts | Number of selected streets | Names of selected streets | Number of regular schools |
|---|---|---|---|---|---|
| Shanghai | 3 out of 16 | Xuhui | 2 out of 12 | Tianping, Fenglin | 11 |
| Minhang | 1 out of 13 | Qibao | 4 | ||
| Qingpu | 2 out of 11 | Yingpu, Xiayang | 8 | ||
| Guangzhou | 1 out of 11 | Huangpu | 9 out of 9 | Huangpu, Hongshan, Yuzhu, Taisha, Wenchong, Nilian, Nangang, Huidong, Changzhou | 21 |
| Changsha | 1 out of 8 | Liuyang | 4 out of 4 | Huaichuan, Jili, Hehua, Guankou | 16 |
| Harbin | 3 out of 9 | Pingfang | 6 out of 6 | Xingjian, Baoguo, Lianmeng, Youxie, Xinjiang, Xinwei | 20 |
| Nangang | 2 out of 18 | Xinchun, Baojilu | 72 | ||
| Daowai | 4 out of 4 | Nongchun, Juyuan, Yongyuan, Mingzhu | 52 | ||
| Beijing | 2 out of 16 | Dongchen | 5 out of 17 | Hepingli, Andingmen, Jiaodaokou, Tiyuguanlu, Longtan | 38 |
| Daxing | 6 out of 22 | Huangxing, Tuanhe, Huangchun, Sunchun, Tiangongyuan, Guanyingshi | 32 | ||
| Chongqing | 3 out of 26 | Jiulongpo | 3 out of 8 | Jiulongpo, Yangjiaping, Shiping | 5 |
| Changshou | 1 out of 7 | Fengcheng | 5 | ||
| Fengdu | 1 out of 2 | Sanhe | 2 | ||
| Chengdu | 2 out of 20 | Pixian | 3 out of 3 | Pitong, Hezuo, Xiyuan | 16 |
| Tianfu | 31 out of 31 | Huayang, Wanan, Xingnong, Zhengxing, Baisha, and others | 31 | ||
| Wenzhou | 2 out of 11 | Pingyang | 2 out of 16 | Xiaojiang, Shuitou | 31 |
| Total | 17 | 82 | 364 |