translation.en: Now, in addition to that, if you were an analyst who was trying to study an epidemic or to predict the adoption of a product, for example, what you could do is you could pick a random sample of the population, also have them nominate their friends and follow the friends and follow both the randoms and the friends.
translation.zh: 现在，在这个基础上， 如果你是分析师，要研究一种传染病 或者预测一个产品的推广， 你能做的是选择一个随机的人群， 让他们任命他们的朋友，然后跟踪他们的朋友， 跟踪随机组和朋友组。