translation.en: If our sample is cherry-picked in some way -- say, we poll only urban voters, or say, in our clinical trials for treatments for heart disease, we include only men -- the results may not generalize to the broader population.
translation.zh: 如果样本是刻意挑选的， 比如说，只抽取城市选民， 或者，在治疗心脏病的临床试验中， 只抽取男性患者， 那结果可能不适用于整个人群。