Reading Statistical Charts

1Summary 重點摘要

Read bar chart, pie chart, line chart, find misleading charts.

2Vocabulary cards Vocabulary

3Step by step Steps

1. Step 1: Pie Chart — see proportionsA pie chart shows what percentage each category takes out of the whole, with the full circle standing for 100%. The angle of each slice = percentage × 360°. For example, in a class of 40 students, if 50% like burgers best, that is 20 students, and the slice angle = 50% × 360° = 180°, exactly half the circle. As a check, all the slice percentages must add up to exactly 100%.
2. Step 2: Pie chart example — daily activity breakdownMing has 10 hours of free time each day: study 4 hours (40%), games 3 hours (30%), sport 2 hours (20%) and other 1 hour (10%). The sizes of the slices show at a glance that studying takes the most time and 'other' the least, and the percentages add up to exactly 100%.
3. Step 3: Line Chart — see trends over timeA line chart shows how data changes over time, such as daily temperature or monthly sales. A line going up means a rise, going down means a fall, and staying level means no change. For example, one week of temperatures: Monday 20°, Tuesday 22°, Wednesday 25°, Thursday 23°, Friday 28°. The overall trend is upward, with only a slight dip on Thursday.
4. Step 4: Common misleading trick — Y-axis doesn't start at 0Many advertising charts start the Y-axis at a number such as 50 instead of 0, so that a tiny change looks like a huge rise on the page - the visual effect is exaggerated. When reading any statistical chart, first check where the Y-axis starts, then judge the true size of the change; do not conclude from the steepness of the line alone, or you may be misled.
5. Step 5: Which chart for whatEach chart has its own purpose, and they must not be mixed up: a pie chart shows how the parts make up the whole; a bar chart compares different categories; a line chart shows a trend over time. For example, you should not use a line chart to compare the heights of several students, because height is not data that changes over time; a bar chart is the right choice, and the wrong chart makes the data hard to interpret.
6. Step 6: Write specific conclusionsDo not just write 'it went up' or 'the most'; quote concrete numbers and state the conclusion, for example 'Ming spends 4 hours a day studying, his largest activity; the weekly temperature rose from 20° to 28° overall, but dipped by 2° on Thursday'. A conclusion backed by numbers is clear and convincing, and this is exactly what earns full marks in an exam.

4Diagrams Diagrams

5Worked example Example

6Common mistakes Mistakes

7Quick check Quick check

8Recap Recap

• Pie chart: each part percent of whole
• Sector angle = percent × 360°
• Line chart: see trend change
• Before compare must see scale clearly
• Vertical axis not start 0 is misleading chart