sampling vertical

例句：

1. 1. We need to sample vertically in order to get a representative sample of the population.
   我们需要进行抽样垂直以获得人口的代表样本。
2. 2. The sampling vertical method is used to collect data from a large population.
   抽样垂直方法用于从大量人群中收集数据。
3. 3. The researcher conducted a sampling vertical study on the effects of air pollution onchildren's health.
   研究者对空气污染对儿童健康的影响进行了抽样垂直研究。