发布时间：2016-04-01 来源：新东方在线 发布人：zolo
9.The Definition Of 'Almost Surely' Is A Mathematical Nightmare
If we were to say that a given event was almost sure to happen, how would you explain that to a small child? Maybe you'd say that the event was practically guaranteed, but then you'd have to explain what "practically" meant in regards to that sentence, which would just confuse things further. It's a tough question because the concept of something being "almost sure" to happen is so vague in and of itself.
Luckily for us all, the concept exists within statistical mathematics, which explains it fully. Unluckily, it's incredibly intimidating at first glance. To quote an online math textbook on the concept:
"In probability theory, a property is said to hold almost surely if it holds for all sample points, except possibly for some sample points forming a subset of a zero-probability event."
In more basic language, that essentially means that even when an event has a 100 percent chance of occurring, it won't necessarily occur. For example, if you flipped a coin a million times, statistically, the odds of the coin landing on heads at least once is essentially one. However, there is an infinitesimally small chance that the coin could land on tails every single time. So although the odds of the event happening are for all intents and purposes guaranteed, it is impossible to say that.