理解“差不多”这一概念，使用粗略估计法。因为我们的教育系统过于重视精确，所以擅长粗略估计这个技能的价值常被低估。这会影响概念化思考。
例如，当被要求计算“38×12”时，大多数人是以缓慢费力的方式计算，而不是简单地把38四舍五入成40，把12四舍五入成10，然后快速地确定答案在400左右。看看
冰激凌店的例子
，想一想，与其费力地把所有关系弄清楚，快速看到各个点之间的大致关系，是多么有用。费力进行精确计算是愚蠢的，但大多数人就是这么做的。
为了做出有效决策，你需要在“差不多”这个层面上理解大多数事物。
当每次有人做一个宏观的“差不多”的陈述，而有些人反驳说“并不总是这样”时，我的本能反应是，我们也许要丢西瓜捡芝麻了，即讨论例外而不是常规，而这将让我们看不到常规。为了帮助桥水的员工避免这种浪费时间的情况，我们的一位刚从大学毕业的投研人员说了一句我经常复述的话：“当你问一个东西对不对而对方告诉你并不完全对时，那它应该大致是对的。”
Understand the concept of “by-and-large” and use approximations. Because our educational system is hung up on precision, the art of being good at approximations is insufficiently valued. This impedes conceptual thinking. For example, when asked to multiply 38 by 12, most people do it the slow and hard way rather than simply rounding 38 up to 40, rounding 12 down to 10, and quickly determining that the answer is about 400. Look at the ice cream shop example and imagine the value of quickly seeing the approximate relationships between the dots versus taking the time to see all the edges precisely. It would be silly to spend time doing that, yet that’s exactly what most people do. “By-and-large” is the level that you need to understand most things in order to make effective decisions. Whenever a big-picture “by-and-large” statement is made and someone replies “Not always,” my instinctual reaction is that we are probably about to dive into the weeds—i.e., into a discussion of the exceptions rather than the rule, and in the process we will lose sight of the rule. To help people at Bridgewater avoid this time waster, one of our just-out-of-college associates coined a saying I often repeat: “When you ask someone whether something is true and they tell you that it’s not totally true, it’s probably by-and-large true.”
