📚 SQA Statistics: Vocabulary Quick Memorisation Guide | 词汇术语速记指南
Mastering statistical terminology is essential for success in SQA Statistics. This guide presents key terms with memorable explanations, helping you quickly recall definitions and apply them in exam contexts. Each section pairs English explanations with direct Chinese translations, making it easier to build a bilingual statistics vocabulary.
掌握统计术语是 SQA 统计学成功的关键。本指南提供重要术语及其便于记忆的解释，帮助您迅速回忆定义并在考试情境中应用。每个部分将英文解释与中文翻译对照排列，让您更轻松地建立双语统计词汇库。
1. Measures of Central Tendency | 集中趋势度量
The mean is the arithmetic average, obtained by summing all data values and dividing by the number of observations. (Memory tip: Mean takes the 'aver-age' of all values.)
均值是算术平均数，通过将所有数据值相加再除以观测数量计算得出。（记忆提示：均值取所有值的“平均”。）
Mean = Σx / n
The median is the middle value when data are ordered. If there is an even number of observations, it is the average of the two middle numbers. (Memory tip: Median sounds like 'medium'—the middle point.)
中位数是数据排序后的中间值。如果观测数为偶数，则是中间两个数的平均值。（记忆提示：中位数听起来像“中间的”点。）
The mode is the value that appears most frequently. A data set can have one mode, more than one mode, or no mode at all. (Memory tip: Mode starts with 'mo' as in 'most'.)
众数是出现次数最多的数值。一个数据集可以有一个众数、多个众数或无众数。（记忆提示：众数以“most”开头——出现最多。）
In symmetric distributions, the mean, median and mode are equal; in skewed data, they differ. The mean is sensitive to outliers, while the median is resistant.
在对称分布中，均值、中位数和众数相等；在偏态数据中它们不同。均值对异常值敏感，而中位数具有较强的抗干扰性。
2. Measures of Spread | 离散程度度量
The range is the simplest measure of spread, calculated as the maximum value minus the minimum value. It only uses two data points, so it can be heavily influenced by outliers.
范围是最简单的离散度量，用最大值减去最小值计算。它仅使用两个数据点，因此极易受异常值影响。
Quartiles divide an ordered data set into four equal parts. The first quartile (Q1) is the median of the lower half, and the third quartile (Q3) is the median of the upper half. The interquartile range (IQR) is Q3 - Q1 and measures the spread of the middle 50%.
四分位数将排序后的数据集分成四等份。第一四分位数（Q1）是下半部分的中位数，第三四分位数（Q3）是上半部分的中位数。四分位距（IQR）为 Q3 - Q1，衡量中间 50% 数据的分散程度。
The standard deviation is a widely used measure of spread that indicates how much the data values deviate from the mean. A larger standard deviation means greater variability. (Memory tip: Standard deviation 'deviates' from the average.)
标准差是一种广泛使用的离散度量，反映数据值偏离均值的程度。标准差越大表示变异性越强。（记忆提示：标准差是指偏离标准平均值。）
s = √[Σ(x - x̄)² / (n - 1)]
For the sample standard deviation, n - 1 is used in the denominator as Bessel's correction to give an unbiased estimate of the population standard deviation.
样本标准差的分母使用 n - 1 作为贝塞尔校正，以得到总体标准差的无偏估计。
3. Types of Data | 数据类型
Qualitative (categorical) data describe attributes or categories, such as eye colour, favourite subject, or type of transport. Quantitative data are numerical and can be measured or counted.
定性（分类）数据描述属性或类别，如眼睛颜色、最喜爱的科目或交通工具类型。定量数据是数值型的，可以测量或计数。
Discrete data arise from counting and can only take specific, isolated values (e.g. number of students, shoe size). Continuous data result from measuring and can take any value within a range (e.g. height, time, temperature).
离散数据来自计数，只能取特定的可数值（如学生人数、鞋码）。连续数据来自测量，可以取一个范围内的任何值（如身高、时间、温度）。
A helpful distinction: if you can say 'there are exactly ... possible values between', it is likely discrete; if there are infinitely many possible values in any interval, it is continuous.
简单的区分方法：如果您能说“在...之间恰好有...个可能的值”，通常是离散型；如果在任何区间内都有无穷多个可能的值，则是连续型。
4. Graphical Representations | 图形表示
A bar chart is used for categorical data, with gaps between the bars to show the categories are distinct. The height of each bar represents the frequency.
条形图用于分类
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