📚 Quick Guide to Key Statistical Terms | 统计词汇术语速记指南
Mastering statistics begins with understanding the language. This guide introduces essential statistical vocabulary for SQA Year 7, pairing clear definitions with simple memory tricks to help you learn faster.
掌握统计从理解语言开始。本指南介绍 SQA 七年级必备统计词汇，用清晰定义搭配简单的记忆窍门，帮助你学得更快。
1. Types of Data | 数据类型
Data is the raw information we collect, and it comes in different forms. The main types you need to know are quantitative (numerical) and qualitative (categorical).
数据是我们收集的原始信息，它有不同形式。你需要了解的主要类型是定量数据（数值型）和定性数据（类别型）。
Quantitative data can be split into discrete and continuous data. Discrete data can only take specific values, usually whole numbers – like the number of goals scored in a match. Continuous data can take any value within a range – like height, weight or temperature.
定量数据可细分为离散数据和连续数据。离散数据只能取特定的值，通常是整数——比如比赛进球数。连续数据可以在一个范围内取任何值——比如身高、体重或温度。
Qualitative data describes qualities or categories, such as favourite colour, type of pet or eye colour. It is often non-numerical.
定性数据描述属性或类别，比如最喜欢的颜色、宠物的种类或眼睛颜色。它通常是非数值的。
Memory trick: Discrete comes from “discrete steps” – think of stairs you can count. Continuous sounds like “continue” without gaps, like time flowing.
记忆窍门：Discrete（离散）来自“离散的步骤”——想象你能数清的台阶。Continuous（连续）听起来像“继续不断”没有间隔，像时间流逝。
2. Averages: Mean, Median, Mode | 平均数：均值、中位数、众数
An average is a single value that represents the centre of a data set. The three most common averages are the mean, median and mode.
平均数是代表一组数据中心的一个单独数值。最常见的三种平均数是平均数（均值）、中位数和众数。
Mean: Add up all values and divide by the number of values. Often called the arithmetic average.
均值：把所有数值加起来，然后除以数值的个数。通常称为算术平均数。
Memory aid: Mean is “mean” because you have to share equally – think of a teacher sharing stickers fairly.
记忆辅助：Mean（均值）之所以“平均”，是因为你必须公平分享——想象一位老师公平地分发贴纸。
Median: The middle value when data is arranged in order. If there are two middle numbers, take the mean of these two.
中位数：将数据按顺序排列后最中间的值。如果有两个中间数，就取这两个数的均值。
Memory aid: Median sounds like “medium” or “middle”. Picture a median strip on a motorway – it splits the road right down the middle.
记忆辅助：Median 听起来像 “medium”（中等）或 “middle”（中间）。想象高速公路的中央分隔带——它正好在路的正中间分开。
Mode: The value that appears most often. A data set can have one mode, more than one mode, or no mode at all.
众数：出现次数最多的数值。一组数据可以有一个众数、多个众数，或者根本没有众数。
Memory aid: Mode sounds like “most”. The word “mode” also means “fashion”, so the mode is the most fashionable number!
记忆辅助：Mode（众数）听起来像 “most”（最多）。Mode 这个词也有“时尚”的意思，所以众数就是最时髦的数字！
3. The Range | 极差
Range measures how spread out the data is. It is the difference between the largest value and the smallest value.
极差衡量数据的离散程度。它是最大值和最小值之间的差值。
For example, in the data set 3, 7, 8, 12, the range is 12 − 3 = 9.
例如，数据集 3, 7, 8, 12，极差是 12 − 3 = 9。
Memory trick: Think of a mountain range – the distance from the lowest valley to the highest peak. Range = max − min.
记忆窍门：想象一条山脉——从最低的山谷到最高的山峰的距离。极差 = 最大值 − 最小值。
4. Frequency and Tally Marks | 频率与计数符号
Frequency tells you how often something occurs. A frequency table organises data by listing items and how many times they appear.
频率告诉你某事发生的次数。频数表通过列出项目及其出现次数来整理数据。
Tally marks are a quick way to record frequency. Each vertical line counts as 1, and every fifth mark is drawn diagonally across the previous four to make a group of five: ||||.
计数符号是记录频率的快捷方式。每一条竖线计为 1，每第五个符号画对角线穿过前四个竖线，形成一个五人组：正。
Using tally marks makes counting much easier when collecting data in real time.
在实时收集数据时，使用计数符号使计数变得容易得多。
Memory aid: Think of tally as “keeping a tally” of goals in a football match – five lines form a gate.
记忆辅助：把 tally（计数）想象成在足球比赛中“记录进球”——五条线组成一个门。
5. Collecting Data: Primary & Secondary | 数据收集：一手数据与二手数据
Primary data is information you collect yourself, firsthand, for a specific purpose. Examples include conducting a survey, measuring classmates’ heights, or timing how long a candle burns.
一手数据是你自己为特定目的直接收集的信息。例如进行调查、测量同学身高或计时蜡烛燃烧的时长。
Secondary data is information that someone else has already collected, such as data from textbooks, websites, or government statistics.
二手数据是他人已经收集好的信息，如教科书、网站或政府统计数据中的数据。
Memory aid: Primary = “first-hand personal”, like your primary school memories. Secondary = “second-hand”, like used clothes.
记忆辅助：Primary = “第一手的个人的”，就像你对小学的记忆。Secondary = “第二手的”，就像二手衣服。
6. Surveys and Questionnaires | 调查与问卷
A survey is a method of gathering information by asking people questions. A questionnaire is the set of questions used in a survey.
调查是通过提问来收集信息的方法。问卷是调查中使用的一组问题。
Questions should be clear, unbiased and easy to answer. A good survey has a mix of closed questions (yes/no or multiple choice) and sometimes open questions for detailed responses.
问题应该清晰、无偏且容易回答。一个好的调查混合了封闭性问题（是/否或选择题），有时也会用开放性问题来获得详细回答。
Pilot your questionnaire on a small group first to check that everybody understands the questions in the same way.
先在一小群人中试填你的问卷，以检查每个人是否以相同的方式理解问题。
7. Bar Charts, Pictograms and Line Graphs | 条形图、象形图和折线图
Different graphs help us visualise data. A bar chart uses bars of equal width
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