📚 Year 7 SQA Statistics: Quick Vocabulary Memorisation Guide | SQA 七年级统计：词汇术语速记指南
Statistics can feel like a new language, but once you learn the key words, everything starts to make sense. This guide breaks down the most important statistical terms you will meet in Year 7 SQA, helping you remember them quickly and use them with confidence.
统计学有时像一门新的语言，但一旦掌握了核心词汇，一切都会变得清晰。这份指南梳理了你在 SQA 七年级统计课程中会遇到的最重要的术语，帮助你快速记忆并自信地运用它们。
1. Mean (Average) | 平均数
The mean is the sum of all the data values divided by the total number of values. It is often called the ‘average’ and gives a central value for a set of numbers.
平均数是将所有数据值相加，再除以数值的总个数。它通常被称为 ‘平均值’，给出一组数据的中心值。
Mean = Sum of all values ÷ Number of values
平均数 = 所有数值之和 ÷ 数值的个数
For example, the mean of 3, 5 and 10 is (3+5+10) ÷ 3 = 6. The mean is sensitive to very high or very low values (outliers).
例如，3、5 和 10 的平均数是 (3+5+10) ÷ 3 = 6。平均数对极高或极低的数值（异常值）很敏感。
2. Median | 中位数
The median is the middle value when the data is placed in order from smallest to largest. If there is an even number of values, the median is the mean of the two middle numbers.
中位数是将数据从小到大排序后处于中间位置的那个数值。如果数据个数是偶数，中位数就是中间两个数的平均数。
For the data set 2, 4, 7, 9, 11, the median is 7. For 2, 4, 7, 9, the median is (4+7) ÷ 2 = 5.5. The median is not affected by outliers.
对于数据集 2, 4, 7, 9, 11，中位数是 7。对于 2, 4, 7, 9，中位数是 (4+7) ÷ 2 = 5.5。中位数不受异常值影响。
3. Mode | 众数
The mode is the value that appears most often in a data set. A set of data can have one mode, more than one mode (bimodal or multimodal), or no mode at all if all values appear only once.
众数是数据集中出现次数最多的数值。一组数据可以有一个众数、多个众数（双众数或多众数），或者如果所有数值都只出现一次，则没有众数。
In the list 3, 5, 5, 7, 9, the mode is 5. In 2, 2, 3, 3, 4, both 2 and 3 are modes. The mode is especially useful for non-numerical data.
在列表 3, 5, 5, 7, 9 中，众数是 5。在 2, 2, 3, 3, 4 中，2 和 3 都是众数。众数对于非数值数据尤其有用。
4. Range | 极差
The range measures how spread out the data is. It is found by subtracting the smallest value from the largest value.
极差衡量数据分散的程度，它是最大值减去最小值得到的差值。
Range = Largest value − Smallest value
极差 = 最大值 − 最小值
For the numbers 3, 8, 12, 15, the range is 15 − 3 = 12. A larger range means the data are more spread out.
对于数字 3, 8, 12, 15，极差是 15 − 3 = 12。极差越大，说明数据越分散。
5. Frequency | 频数
Frequency is the number of times a particular value or category occurs in a data set. A frequency table helps to organise data clearly.
频数是某个特定数值或类别在数据集中出现的次数。频数表有助于清晰地整理数据。
For example, if you survey 20 classmates’ favourite colours and 8 say ‘blue’, then the frequency of blue is 8. Tally marks are often used to record frequency.
例如，如果你调查了 20 个同学最喜欢的颜色，有 8 人选了 ‘蓝色’，那么蓝色的频数就是 8。通常用画记符号来记录频数。
6. Data Types: Qualitative and Quantitative | 数据类型：定性数据与定量数据
Qualitative data describes qualities or categories that cannot be measured with numbers, such as eye colour, type of pet or favourite film. Quantitative data is numerical and can be measured or counted, such as height, age or test scores.
定性数据描述的是无法用数字衡量的属性或类别，例如眼睛颜色、宠物类型或最喜欢的电影。定量数据是数值型的，可以测量或计数，例如身高、年龄或考试分数。
Remember: Qualitative = descriptions and categories; Quantitative = numbers. This distinction helps you decide which graph or average to use.
记住：定性数据 = 描述和类别；定量数据 = 数字。这种区分有助于你决定使用哪种图表或平均数。
7. Discrete and Continuous Data | 离散数据与连续数据
Discrete data can only take certain, separate values – often whole numbers. Examples include the number of students in a class or the number of cars in a car park. You cannot have half a student.
离散数据只能取特定的、相互分离的值 —— 通常是整数。例如班级里的学生人数或停车场里汽车的数量。你不可能有半个学生。
Continuous data can take any value within a range and can be measured to different levels of precision. Height, weight, temperature and time are continuous. You can have a height of 142.5 cm.
连续数据可以在一定范围内取任意值，并且可以测量到不同的精度。身高、体重、温度和时间都是连续数据。你可以有 142.5 厘米的身高。
8. Probability (Likelihood) | 概率（可能性）
Probability is a measure of how likely an event is to happen. It is always a number between 0 (impossible) and 1 (certain). Probability can be written as a fraction, decimal or percentage.
概率是用来衡量某个事件发生可能性的量度。它总是一个介于 0（不可能）和 1（必然）之间的数字。概率可以用分数、小数或百分数表示。
Probability = Number of favourable outcomes ÷ Total number of possible outcomes
概率 = 有利结果的数量 ÷ 所有可能结果的总数
Flipping a fair coin and getting heads has a probability of ½ or 0.5. The sum of probabilities for all possible outcomes is always 1.
抛一枚公平硬币得到正面的概率是 ½ 或 0.5。所有可能结果的概率之和总是等于 1。
9. Sample and Population | 样本与总体
A population is the entire group that you want to find out about. A sample is a smaller group selected from the population to represent it. Sampling is used because it is often impossible or impractical to survey everyone.
总体是你想要了解的整个群体。样本是从总体中选取的、用以代表总体的一个较小群体。使用抽样调查，是因为调查每个人往往不可能或不现实。
If you ask 50 Year 7 students about their homework habits, those 50 are the sample, and all Year 7 students in the school are the population. A fair sample should be random to avoid bias.
如果你就家庭作业习惯询问了 50 名七年级学生，这 50 名学生就是样本，而学校里所有七年级学生就是总体。公平的样本应当是随机的，以避免偏差。
10. Tally Chart | 计数表
A tally chart is a quick way to record data by drawing marks. Each mark stands for one item, and the fifth mark is drawn diagonally across the previous four to make a group of five. This makes counting frequencies much faster and more accurate.
计数表是通过画记符号来快速记录数据的方法。每个符号代表一个项目，第五个符号会斜向画过前面四个，形成一组五个。这让统计频数变得更快、更准确。
A typical tally for 7 would be: |||| || (a bundle of five plus two). Tally charts are often turned into frequency tables before drawing a graph.
7 的典型计数记号为： 卌 || （一组五个加上两个）。计数表通常在绘制图表前被整理成频数表。
11. Bar Chart and Pictogram | 条形图与象形图
A bar chart uses rectangular bars to represent frequencies. The height or length of each bar shows the number. Bars can be vertical or horizontal, and they are separated by gaps. Bar charts are ideal for showing discrete or categorical data.
条形图用矩形条来表示频数。每个矩形的高度或长度显示该数字。条形可以垂直或水平排列，并且条与条之间有间隙。条形图适合展示离散数据或分类数据。
A pictogram uses small pictures or symbols to represent data. Each symbol stands for a certain number of items, and a key shows what one symbol is worth. Pictograms are very visual and can be easier to understand at a glance.
象形图使用小图片或符号来表示数据。每个符号代表一定数量的项目，图例会说明一个符号所代表的数量。象形图非常直观，一眼看上去更容易理解。
12. Outlier | 异常值
An outlier is a data value that is much larger or much smaller than most of the other values in the set. Outliers can affect the mean dramatically, making it less representative of the data as a whole.
异常值是指数据集中远大于或远小于其他大多数数值的那个数据。异常值会显著影响平均数，使其不那么能代表整体数据。
If a class’s test scores are 55, 58, 60, 61, 62 and 98, the score 98 is an outlier. The median and mode are often better measures of central tendency when outliers are present.
如果一个班的测验分数为 55、58、60、61、62 和 98，那么 98 分就是异常值。当存在异常值时，中位数和众数往往是更好的集中趋势度量。
Here is a quick summary table of the key terms covered in this guide. Use it as a fast revision aid.
下面是本指南所涉及关键术语的快速汇总表，可作为快速复习的辅助工具。
| Term | 中文 | Simple meaning |
|---|---|---|
| Mean | 平均数 | Sum ÷ number of values |
| Median | 中位数 | Middle value when ordered |
| Mode | 众数 | Most frequent value |
| Range | 极差 | Largest − smallest |
| Frequency | 频数 | How many times something occurs |
| Qualitative | 定性数据 | Describes categories or qualities |
| Quantitative | 定量数据 | Numerical, can be measured |
| Discrete | 离散数据 | Separate, countable values |
| Continuous | 连续数据 | Any value in a range |
| Probability | 概率 | Chance of an event, 0 to 1 |
| Population | 总体 | Whole group of interest |
| Sample | 样本 | Part of population chosen to represent it |
| Tally Chart | 计数表 | Marks grouped in fives for counting |
| Bar Chart | 条形图 | Bars to show frequency, gaps between |
| Pictogram | 象形图 | Pictures or symbols to show data |
| Outlier | 异常值 | A value very different from the rest |
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