当随机化不可行时，匹配方法可以是一个强大的工具。
"Matching methods can be a powerful tool when randomization is not possible."
Sometimes it’s the people no one imagines anything of who do the things that no one can imagine.
In the context of computational learning, the concept of 'probably approximately correct' (PAC) learning provides a framework for understanding the efficiency and feasibility of learning algorithms.
"History is not just what happened, but what people thought and felt about it."
"Identity is not just about where you come from, but also about where you are going."