🎲 随机事件：不一定发生的事🎲 Random Events: the things that may not happen
上一片，我们把已经发生的数据画成了图。可有些事还没发生——明天会下雨吗？这一片说说“不一定”的事。Last leaf we drew charts of data that had already happened. But some things haven’t happened yet — will it rain tomorrow? This leaf is about the “maybe”.
第 1 步：一定、不可能、可能Step 1: certain, impossible, possible
一件事还没发生时，它属于哪一种？When something hasn’t happened yet, which kind is it?
抛一枚硬币：正面朝上不是必然的，也不叫不可能——它可能发生，也可能不发生，这叫随机事件。三类事件正好是三兄弟：太阳从东边升起是必然事件（一定发生）；太阳从西边升起是不可能事件（一定不发生）；硬币正面朝上是随机事件（不一定）。Flip a coin: heads isn’t certain, and it isn’t impossible either — it may happen, and it may not. That is a random event. Events come in three brothers: the sun rising in the east is certain (always happens); the sun rising in the west is impossible (never happens); a coin landing heads is random (not sure at all).
天气预报里那句“可能下雨”，到底在说什么？That “maybe rain” in the forecast — what is it really saying?
第 2 步：“明天可能下雨”是什么意思Step 2: what “maybe rain tomorrow” means
预报说“降水概率 70%”，意思是：在同样的天气条件下，100 次里大约有 70 次会下雨。它没说“明天一定下雨”，也没说“明天不下雨”——它老老实实承认了“不一定”，还给这份“不一定”配了一个数字。When the forecast says “70% chance of rain”, it means: under the same weather conditions, about 70 out of 100 times it would rain. It does not say “it will definitely rain”, nor “it definitely won’t” — it simply admits the “maybe”, and gives that “maybe” a number.
那“可能性”本身，能量出大小吗？So can “possibility” itself be measured?
第 3 步：概率——给可能性一把尺子Step 3: probability — a ruler for possibility
能。概率是 0 到 1 之间的一把尺子：0 那头是不可能，1 那头是必然，中间全是随机。转盘上蓝色占了一半，转中蓝色的概率大约是 0.5；蓝色区域越大，转中的概率就越大。随机事件的概率，永远落在 0 和 1 之间。Yes. Probability is a ruler that runs from 0 to 1: 0 is impossible, 1 is certain, and everything in between is random. If blue takes half of the prize wheel, the chance of landing on blue is about 0.5; the bigger the blue area, the higher the chance. The probability of a random event always lies between 0 and 1.
🎮 你来当分类员（1 分钟）🎮 Your turn: sort the events (1 minute)
道理讲完了。下面 4 张事件卡，把它们分进“一定发生 / 可能发生 / 不可能发生”——小心，里面藏着脑筋急转弯。Theory done. Here are 4 event cards — sort each into “certain / possible / impossible”. Careful: a trick question is hiding in there.
一句话记住它：事件分三兄弟——必然、不可能、随机；随机事件的概率在 0 到 1 之间。Remember it in one line: events come in three brothers — certain, impossible, random; a random event’s probability lies between 0 and 1.
必然事件一定发生，概率 = 1（如明天太阳从东边升起）A certain event always happens, probability = 1 (e.g. the sun rises in the east tomorrow)不可能事件一定不发生，概率 = 0（如太阳从西边升起）An impossible event never happens, probability = 0 (e.g. the sun rises in the west)随机事件可能发生也可能不发生，概率在 0 到 1 之间（如抛硬币正面朝上）A random event may happen or not, probability between 0 and 1 (e.g. a coin landing heads)
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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