High-Frequency Topics and Common Mistake Analysis for CAIE A-Level Statistics | A-Level CAIE 统计：高频考点与易错题分析

📚 High-Frequency Topics and Common Mistake Analysis for CAIE A-Level Statistics | A-Level CAIE 统计：高频考点与易错题分析

This revision guide identifies the most frequently examined topics in CAIE A-Level Probability & Statistics (Paper 5 and Paper 6) and analyses the mistakes that cost candidates marks. Each section pairs concise explanation with common errors, so you can target both knowledge and exam technique.

本复习指南梳理 CAIE A-Level 概率与统计（Paper 5 与 Paper 6）最高频考点，并分析考生常见失分错误。每节以简洁讲解搭配易错提醒，帮助你有针对性地提升知识与应试技巧。

1. Exam Weighting and Command Words | 考点权重与指令词

Before revising individual topics, check the syllabus weighting. In Statistics 1, representation of data, probability, discrete random variables and the normal distribution dominate; in Statistics 2, the Poisson distribution, continuous random variables, sampling and hypothesis tests carry most marks.

复习各专题前，先看清考纲权重。统计 1 中，数据表示、概率、离散随机变量和正态分布占主导；统计 2 中，泊松分布、连续随机变量、抽样和假设检验占分最多。

Common mistake: candidates often answer what they know rather than what the command word asks. ‘State’ requires no working; ‘verify’ requires substitution; ‘comment’ requires comparison in context.

常见错误：考生常答自己熟悉的内容，而忽略指令词要求。’State’ 不需要过程；’verify’ 需要代入验证；’comment’ 要求在题目情境中进行比较。

Always write down the distribution and parameters before calculating, for example X ~ B(10, 0.3) or X ~ N(50, 4²). This helps you choose the correct formula and earns method marks.

计算前先写出分布及参数，例如 X ~ B(10, 0.3) 或 X ~ N(50, 4²)。这有助于选择正确公式并获得方法分。

2. Representation of Data | 数据表示

Candidates must be able to read and construct histograms, cumulative frequency graphs, box-and-whisker plots and stem-and-leaf diagrams. A histogram plots frequency density on the vertical axis, not frequency.

考生必须会读、会画直方图、累积频率图、箱线图和茎叶图。直方图纵轴是频率密度，不是频数。

Frequency density = Frequency ÷ Class width

For unequal class widths, using frequency directly makes the diagram misleading. Always calculate frequency density for each bar and label the axis correctly.

当组距不等时，直接使用频数会误导图形。每个条形都要计算频率密度，并正确标注坐标轴。

When estimating the median from a cumulative frequency graph, read at ½n, not ½(maximum frequency). For grouped data, use linear interpolation only when the question requires an estimate from a table.

从累积频率图估计中位数时，应在 ½n 处读数，而不是最大频率的一半。对于分组数据，仅在题目要求根据表格估计时使用线性插值。

Common mistake: confusing quartiles with percentiles. Q1 is the 25th percentile, Q2 is the median, Q

Published by TutorHao | A-Level 统计 Revision Series | aleveler.com

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