📚 Understanding Probability | 理解概率
Probability is a fundamental concept in IGCSE Mathematics that helps us measure uncertainty and make informed predictions. In everyday life, from weather forecasts to game strategies, probability plays a crucial role. For Edexcel IGCSE, understanding probability means mastering terminology, calculating chances, and applying rules such as the addition and multiplication rules, tree diagrams, and conditional probability. This revision guide covers all essential topics, providing clear explanations, step-by-step methods, and exam-focused tips to boost your confidence.
概率是IGCSE数学中的一个基本概念，帮助我们衡量不确定性并做出合理预测。在日常生活中，从天气预报到游戏策略，概率都起着至关重要的作用。针对Edexcel IGCSE，理解概率意味着掌握术语、计算机会，并运用加法和乘法法则、树状图以及条件概率等规则。本复习指南涵盖所有重要主题，提供清晰的解释、分步方法和以考试为导向的技巧，增强你的信心。
1. Definition and Basic Formula | 定义和基本公式
Probability quantifies the likelihood of an event occurring. For any event A, the theoretical probability P(A) is given by:
P(A) = number of favourable outcomes / total number of outcomes
The set of all equally likely outcomes is called the sample space. For example, when rolling a fair six-sided die, the sample space is {1, 2, 3, 4, 5, 6}. The probability of rolling a number greater than 4 (i.e., 5 or 6) is 2/6, which simplifies to 1/3. Probabilities are typically expressed as fractions in their simplest form, but decimals and percentages are also acceptable unless stated otherwise. Always check that your fraction is fully simplified – marks are often awarded for final answers in lowest terms.
概率量化了事件发生的可能性。对于任何事件A，理论概率P(A)由下式给出：
P(A) = 有利结果的数量 / 总结果的数量
所有等可能结果的集合称为样本空间。例如，抛掷一个公平的六面骰子时，样本空间为{1, 2, 3, 4, 5, 6}。掷出大于4的点数（即5或6）的概率是2/6，化简为1/3。概率通常用最简分数表示，但除非另有说明，小数和百分数也可接受。务必检查你的分数是否完全化简——最终答案化为最简通常可得分数。
2. Sample Space and Outcomes | 样本空间与结果
find probabilities effectively, we must be able to list or describe all possible outcomes – ed events, such as rolling a die and tossing a coin, a sample space diagram (or a grid) helps visualise all possibilities. Counting outcomes systematically reduces errors and ensures no outcome is missed. Always ask yourself: are the outcomes equally likely? If not, a simple list may not directly give probabilities.
为了有效求概率，我们必须能够列出或描述所有可能的结果——样本空间。一种常用方法是创建系统列表或双向表格。例如，抛掷两枚硬币时，样本空间可表示为{HH, HT, TH, TT}。每个结果出现可能性相等，因此P(至少有一个正面) =
Published by TutorHao | IGCSE Mathematics Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
或截图后用「扫一扫 → 相册」选择本图