现在做到哪了
书籍
目前有 5 本书、9 章，免费阅读。
它有什么不同
一节课，实际是这样开始的
导师Suppose you wanted to know the average height of every adult in your country. Measuring all of them isn't realistic. What would you do instead?
Measure some of them, I guess? Like a smaller group, and just use that average. I don't know how you'd pick who, or how many you'd need.
导师Exactly — you wouldn't measure all of them. You'd pick a smaller group and work with that. In statistics, there's a specific word for that smaller group you actually measure. What do you think it's called?
摘自第一章《Sampling and Data》的一节测试课。导师的话是导师自己说的；这一轮的学生是用于测试的模拟学生，不是真人。课本目前只有英文版，所以对话也是英文。
哪些免费，哪些以后收费
阅读永远免费，对所有人开放，不需要账户：多一位读者，我们不多花一分钱。导师的对话每一轮都要真金白银，所以各种教学模式以后会采用订阅制，并保留一份免费额度，让你不付费也能开始。今天没有任何可以购买的东西。
Shello 不教医学、法律、金融和心理健康，也不会就你本人的健康、金钱或法律处境给出建议，无论当时打开的是哪一章。统计课会教你什么是期望值，但不会告诉你这一注该不该下。