📚 IGCSE CCEA Statistics: Vocabulary Glossary Memory Guide | IGCSE CCEA 统计：词汇术语速记指南
This guide breaks down the essential terms in the CCEA IGCSE Statistics specification into quick, memorable clusters. Use the paired definitions and memory hooks to revise actively before your exam.
本指南将 CCEA IGCSE 统计学大纲中的核心术语分成便于记忆的小组。通过中英对照的定义和记忆线索，帮助你在考试前高效复习。
1. Core Statistical Vocabulary | 核心统计词汇
Population means the entire set of individuals or items that you want to study. A sample is a smaller group selected from the population. A census collects data from every member of the population.
总体指你想研究的全部个体或项目。样本是从总体中选出的较小群体。普查则收集总体中每一个成员的数据。
A parameter is a numerical summary of a population, while a statistic is a numerical summary calculated from a sample. Raw data are unprocessed values before being organised into tables or charts.
参数是总体的数值概括，而统计量是从样本计算出的数值概括。原始数据是尚未整理成表格或图表的原始数值。
Memory hook: ‘Population = whole pie, sample = one slice, census = eat the whole pie.’
记忆线索：’总体是整块饼，样本是一块切片，普查是吃掉整块饼。’
2. Types of Data | 数据类型
Qualitative data describe qualities or categories, such as colour, gender, or type of transport. Quantitative data are numerical and can be either discrete or continuous.
定性数据描述性质或类别，例如颜色、性别或交通方式。定量数据是数值型数据，可以是离散型或连续型。
Discrete data can only take certain values, usually counted, such as the number of cars in a car park. Continuous data can take any value within a range, usually measured, such as height or time.
离散型数据只能取某些特定值，通常是计数得到的，例如停车场里的汽车数量。连续型数据可以在一个范围内取任意值，通常是测量得到的，例如身高或时间。
Think: ‘Quality = category, Quantity = number.’ Discrete = counted, continuous = measured.
记忆：’Quality 质量 = 分类，Quantity 数量 = 数字。’ 离散型 = 可数，连续型 = 可测量。
3. Data Collection Methods | 数据收集方法
Primary data are collected by you or your team for a specific purpose, such as a questionnaire, interview, or experiment. Secondary data are data that already exist, such as government reports, textbooks, or websites.
原始数据是你或你的团队为特定目的收集的数据，如问卷、访谈或实验。二手数据是已经存在的数据，如政府报告、教科书或网站资料。
Common primary collection tools include questionnaires, interviews, observations, and experiments. Each has strengths: questionnaires reach many people quickly, while interviews allow deeper follow-up.
常见的原始数据收集工具包括问卷、访谈、观察和实验。每种方法都有优点：问卷能快速覆盖大量人群，而访谈可以进行更深入的追问。
A pilot survey is a small trial run of a questionnaire used to identify unclear or biased questions before the main data collection.
试点调查是问卷的小规模试运行，用于在正式收集数据前发现不清晰或有偏差的问题。
4. Sampling Techniques | 抽样方法
Random sampling gives every member of the population an equal chance of selection, which helps reduce bias. Stratified sampling divides the population into groups called strata and samples proportionally from each group.
随机抽样让总体中每个成员都有相同被选中的机会，有助于减少偏差。分层抽样将总体分成称为层的组，并按比例从每组中抽样。
Systematic sampling selects every nth item after a random starting point. Cluster sampling selects whole groups or clusters at random. Quota sampling fills fixed numbers from subgroups but is not random.
系统抽样在随机起点后每隔 n 个抽取一个。整群抽样随机选取整个群体。配额抽样按固定人数从子群中选取，但不是随机抽样。
Convenience sampling uses people who are easy to reach, such as friends or people in the same street, and often introduces bias. A sampling frame is a list of all members of the population from which a sample can be drawn.
便利抽样使用容易接触到的人，例如朋友或同一条街上的人，通常会引入偏差。抽样框是总体中所有成员的名单，样本可以从中抽取。
5. Measures of Central Tendency | 集中趋势度量
Mean is the sum of all values divided by the number of values. It is calculated as:
平均数是所有数值之和除以数值个数。计算公式为：
Mean: x̄ = Σx / n
Median is the middle value when data are ordered from smallest to largest. Mode is the most frequent value or category.
中位数是将数据从小到大排列后的中间值。众数是出现频率最高的值或类别。
For grouped data, the modal class is the class with the highest frequency, and the mean can be estimated using midpoints. The median can be read from a cumulative frequency curve.
对于分组数据，众数组是频数最高的组，平均数可用组中点进行估算。中位数可从累积频数曲线中读取。
The mean is sensitive to outliers, while the median is more robust. Choose the median when data are skewed or contain extreme values.
平均数对异常值敏感，而中位数更具稳健性。当数据偏斜或含有极端值时，应选择中位数。
6. Measures of Spread | 离散程度度量
Range = largest value – smallest value. It is quick to calculate but affected by outliers. Interquartile range (IQR) = upper quartile Q₃ – lower quartile Q₁, and it measures the spread of the middle 50% of data.
极差 = 最大值 – 最小值。它计算简单但受异常值影响。四分位距（IQR） = 上四分位数 Q₃ – 下四分位数 Q₁，衡量中间 50% 数据的分散程度。
Percentiles divide ordered data into 100 equal parts. The lower quartile Q₁ is the 25th percentile, the median is the 50th percentile, and the upper quartile Q₃ is the 75th percentile.
百分位数将有序数据分成 100 等份。下四分位数 Q₁ 是第 25 百分位数，中位数是第 50 百分位数，上四分位数 Q₃ 是第 75 百分位数。
Variance and standard deviation measure how far values vary from the mean. Standard deviation σ is the square root of the variance, written as:
方差和标准差衡量各数值与平均数的偏离程度。标准差 σ 是方差的平方根，写作：
σ = √(Σ(x – x̄)² / n)
A common outlier test uses the rule: any value below Q₁ – 1.5 × IQR or above Q₃ + 1.5 × IQR may be an outlier.
常用的异常值判断规则是：任何低于 Q₁ – 1.5 × IQR 或高于 Q₃ + 1.5 × IQR 的值都可能是异常值。
7. Frequency Distributions |
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