📚 Year 9 Edexcel Statistics: Unit Test Mock Exam Walkthrough | Year 9 Edexcel 统计：单元测试模拟卷解析
Welcome to the mock exam walkthrough for Year 9 Edexcel Statistics. This article provides a complete breakdown of a typical unit test, covering core topics such as data types, sampling, charts, averages, probability and more. Use this guide to revise, spot common mistakes, and build exam confidence.
欢迎阅读 Year 9 Edexcel 统计模拟卷解析。本文将完整拆解一套典型的单元测试，涵盖数据类型、抽样、图表、平均数、概率等核心内容。使用本指南进行复习，发现常见错误，建立考试信心。
1. Mock Exam Overview & Top Tips | 模拟卷概述与高分技巧
This mock exam consists of 9 questions worth a total of 50 marks, to be completed in 45 minutes. The questions test core Year 9 statistics topics and follow the style of the Edexcel specification.
本模拟卷包含9道题目，满分50分，限时45分钟完成。题目考查 Year 9 统计核心主题，遵循 Edexcel 考试风格。
Exam tip 1: Read each question twice and underline command words such as ‘calculate’, ‘compare’, ‘draw’ or ‘explain’.
考试技巧1：仔细阅读每道题目，标出指令词，如“计算”、“比较”、“绘制”或“解释”。
Tip 2: Show all working clearly. Even if the final answer is wrong, you can earn method marks for correct steps.
技巧2：清晰展示所有计算步骤。即使最终答案错误，正确的过程也能获得步骤分。
Tip 3: Include units on axes, charts and final answers where appropriate.
技巧3：在坐标轴、图表和最终答案中标注合适的单位。
Tip 4: Use a ruler to draw straight lines in graphs and bar charts.
技巧4：绘制图表中的直线和条形图时使用直尺。
Tip 5: In comparison questions, always refer to both an average and a measure of spread, such as the range.
技巧5：在比较类问题中，务必同时引用平均数（集中趋势）和离散程度（如极差）。
2. Question 1: Types of Data | 问题1：数据类型
Question: Classify each variable as qualitative or quantitative. For quantitative variables, state whether they are discrete or continuous. a) Number of siblings b) Favourite colour c) Height in cm d) Time taken to run 100 m e) Shoe size.
题目：将下列变量分类为定性或定量。对于定量变量，指出其是离散还是连续。a) 兄弟姐妹数量 b) 最喜欢的颜色 c) 身高（厘米） d) 跑100米所用时间 e) 鞋码。
a) Number of siblings – Quantitative, discrete. It is countable and takes whole-number values.
a) 兄弟姐妹数量 – 定量、离散。因为可数且取整数值。
b) Favourite colour – Qualitative. Colours are non-numerical categories.
b) 最喜欢的颜色 – 定性。颜色属于非数值类别。
c) Height in cm – Quantitative, continuous. Height can be measured to any degree of accuracy and can take any value within a range.
c) 身高（厘米） – 定量、连续。身高可以被测量到任意精度，可在区间内取任意值。
d) Time taken to run 100 m – Quantitative, continuous. Time is measured and can take any value in an interval.
d) 跑100米所用时间 – 定量、连续。时间可测量，能在区间内取任意值。
e) Shoe size – Quantitative, discrete. Although shoes may have half sizes, shoe size is usually a set of distinct values and is therefore discrete.
e) 鞋码 – 定量、离散。虽然鞋码有半码，但通常由一组特定的可数值构成，因此属于离散变量。
3. Question 2: Sampling Methods | 问题2：抽样方法
Question: A headteacher wants to survey 50 students from a school of 800. Describe how to obtain a stratified sample by year group, using the population data: Year 7 – 200, Year 8 – 200, Year 9 – 200, Year 10 – 100, Year 11 – 100.
题目：一位校长想从800名学生中抽查50名。描述如何按年级进行分层抽样，已知各年级人数：Year 7 – 200，Year 8 – 200，Year 9 – 200，Year 10 – 100，Year 11 – 100。
Step 1: Find the total population, which is 800.
第一步：确定总体人数为800。
Step 2: Calculate the sample fraction for each stratum using the formula: (stratum size ÷ total population) × sample size.
第二步：计算每个层的样本量，公式为：(层人数 ÷ 总人口) × 样本量。
Year 7: (200 ÷ 800) × 50 = 0.25 × 50 = 12.5, round to 13 students.
Year 7: (200 ÷ 800) × 50 = 0.25 × 50 = 12.5，四舍五入至13名学生。
Year 8: (200 ÷ 800) × 50 = 13 students.
Year 8: (200 ÷ 800) × 50 = 13名学生。
Year 9: (200 ÷ 800) × 50 = 13 students.
Year 9: (200 ÷ 800) × 50 = 13名学生。
Year 10: (100 ÷ 800) × 50 = 0.125 × 50 = 6.25, round to 6 students.
Year 10: (100 ÷ 800) × 50 = 0.125 × 50 = 6.25，四舍五入至6名学生。
Year 11: (100 ÷ 800) × 50 = 6.25, round to 6 students.
Year 11: (100 ÷ 800) × 50 = 6.25，四舍五入至6名学生。
Step 3: Check the total: 13+13+13+6+6 = 51. Adjust down by one student from one group (e.g. 12 from Year 7) to reach exactly 50.
第三步：检查总和：13+13+13+6+6 = 51。可以从某个组中减少1人（例如Year 7取12人），以达到恰好50人。
Step 4: Within each year group, select the required number of students using simple random sampling (e.g. using a random number generator).
第四步：在每个年级内，使用简单随机抽样（例如采用随机数生成器）选择所需数量的学生。
4. Question 3: Frequency Tables and Bar Charts | 问题3：频率表与条形图
Question: A survey asked 30 students how they travel to school. The results were: Walk – 12, Bus – 10, Car – 5, Bicycle – 3. a) Complete the frequency table. b) Draw a bar chart for the data.
题目：一项调查询问了30名学生上学的交通方式。结果如下：步行 – 12，公交 – 10，小汽车 – 5，自行车 – 3。a) 完成频率表。b) 根据数据绘制条形图。
a) The completed frequency table is shown below. Mode of transport and frequency columns should be clearly labelled. Total frequency is 30.
a) 完整的频率表如下所示。应清晰标注交通方式和频数列，总频数为30。
| Mode of transport | Frequency |
|---|---|
| Walk | 12 |
| Bus | 10 |
| Car | 5 |
| Bicycle | 3 |
| Total | 30 |
b) When drawing the bar chart, place the categories on the horizontal axis and frequency on the vertical axis. Bars must be of equal width, with gaps between them. Label both axes and give the chart a title, e.g. ‘Travel to school’. The bars should be drawn accurately according to the frequency scale, and Walk (12) will be the tallest bar.
b) 绘制条形图时，将类别放在横轴，频数放在纵轴。条形宽度应相等，且条与条之间留有间隙。标注两个轴并添加图表标题，如“上学交通方式”。条形根据频数比例精确绘制，“步行”条形最高（12）。
5. Question 4: Pie Charts and Proportions | 问题4：饼图与比例
Question: 40 people were asked their favourite colour. The results: Red – 10, Blue – 15, Green – 8, Yellow – 7. Calculate the angle for each sector and construct a pie chart.
题目：40人被问及最喜欢的颜色。结果：红色 – 10，蓝色 – 15，绿色 – 8，黄色 – 7。计算每个扇形的角度并绘制饼图。
The total frequency is 40. The angle for each sector is calculated using: (frequency ÷ total) × 360°.
总频数为40。每个扇形的角度计算公式为：(频数 ÷ 总数) × 360°。
Red: (10 ÷ 40) × 360° = 0.25 × 360° = 90°.
红色：(10 ÷ 40) × 360° = 0.25 × 360° = 90°。
Blue: (15 ÷ 40) × 360° = 0.375 × 360° = 135°.
蓝色：(15 ÷ 40) × 360° = 0.375 × 360° = 135°。
Green: (8 ÷ 40) × 360° = 0.2 × 360° = 72°.
绿色：(8 ÷ 40) × 360° = 0.2 × 360° = 72°。
Yellow: (7 ÷ 40) × 360° = 0.175 × 360° = 63°.
黄色：(7 ÷ 40) × 360° = 0.175 × 360° = 63°。
Check: 90° + 135° + 72° + 63° = 360°. Draw the pie chart using a protractor, label each sector or use a key. Give the chart a title, e.g. ‘Favourite colours of 40 people’.
检查：90° + 135° + 72° + 63° = 360°。使用量角器绘制饼图，为每个扇形标注标签或使用图例。添加图表标题，如“40人最喜欢的颜色”。
6. Question 5: Stem-and-Leaf Diagrams | 问题5：茎叶图
Question: The heights (in cm) of 14 boys and 14 girls in Year 9 are recorded. Boys: 152, 158, 160, 163, 165, 165, 167, 170, 172, 175, 178, 180, 182, 185. Girls: 148, 150, 153, 155, 158, 160, 162, 164, 165, 167, 170, 172, 175, 177. Construct a back-to-back stem-and-leaf diagram and find the median height for each group.
题目：记录了14名男生和14名女生的身高（cm）。男生：152, 158, 160, 163, 165, 165, 167, 170, 172, 175, 178, 180, 182, 185。女生：148, 150, 153, 155, 158, 160, 162, 164, 165, 167, 170, 172, 175, 177。绘制背靠背茎叶图，并求每组身高的中位数。
Use a stem of tens and leaves as units. The key: 15 | 2 means 152 cm. For the boys, leaves on the left; for girls, leaves on the right of the stem. Order leaves from smallest to largest.
使用十位数为茎、个位数为叶。图例：15 | 2 表示 152 cm。男生叶在茎左侧，女生叶在茎右侧。叶片从小到大排列。
The median position for n=14 is the (14+1)/2 = 7.5th value, so we average the 7th and 8th ordered values.
当 n=14 时，中位数位置为 (14+1)/2 = 7.5，因此取第7和第8个有序数值的平均值。
Boys ordered: 152, 158, 160, 163, 165, 165, 167, 170, 172, 175, 178, 180, 182, 185. The 7th value is 167, 8th is 170. Median = (167+170) ÷ 2 = 168.5 cm.
男生排序：152, 158, 160, 163, 165, 165, 167, 170, 172, 175, 178, 180, 182, 185。第7个值为167，第8个为170。中位数 = (167+170) ÷ 2 = 168.5 cm。
Girls ordered: 148, 150, 153, 155, 158, 160, 162, 164, 165, 167, 170, 172, 175, 177. The 7th is 162, 8th is 164. Median = (162+164) ÷ 2 = 163 cm.
女生排序：148, 150, 153, 155, 158, 160, 162, 164, 165, 167, 170, 172, 175, 177。第7个为162，第8个为164。中位数 = (162+164) ÷ 2 = 163 cm。
7. Question 6: Mean, Median, Mode, and Range | 问题6：平均数、中位数、众数与极差
Question: The scores of a student in 6 maths tests are: 5, 7, 8, 8, 10, 12. Calculate the mean, median, mode and range.
题目：一名学生在6次数学测试中的得分为：5, 7, 8, 8, 10, 12。计算平均数、中位数、众数和极差。
Mean: Add all values and divide by the number of values.
平均数：将所有值相加后除以数值个数。
Mean = (5 + 7 + 8 + 8 + 10 + 12) ÷ 6 = 50 ÷ 6 ≈ 8.33
Median: Arrange in order (already ordered) and find the middle. For an even number of values, average the two middle numbers. The 3rd value is 8, 4th is 8.
中位数：按顺序排列（已排序）并找到中间值。因为数值个数为偶数，取中间两个数的平均值。第3个为8，第4个为8。
Median = (8 + 8) ÷ 2 = 8
Mode is the value that appears most frequently: 8 appears twice, so mode = 8.
众数是出现频率最高的值：8出现两次，因此众数 = 8。
Range = highest value − lowest value = 12 − 5 = 7.
极差 = 最大值 − 最小值 = 12 − 5 = 7。
8. Question 7: Scatter Graphs and Correlation | 问题7：散点图与相关性
Question: The table shows the number of hours 8 students spent revising and their test scores. Hours: 1, 2, 2, 3, 4, 5, 6, 7. Scores: 40, 45, 50, 55, 60, 70, 75, 85. a) Draw a scatter graph. b) Describe the correlation. c) Draw a line of best fit and estimate the score for a student who revised for 3.5 hours.
题目：表格显示了8名学生复习的小时数及测试分数。小时数：1, 2, 2, 3, 4, 5, 6, 7。分数：40, 45, 50, 55, 60, 70, 75, 85。a) 绘制散点图。b) 描述相关性。c) 绘制最佳拟合线，并估计复习3.5小时的分数。
b) The plotted points show an upward trend, indicating a positive correlation. As revision hours increase, test scores tend to increase.
b) 绘出点后呈现上升趋势，表明正相关。随着复习时间增加，测试分数倾向于提高
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