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By the end of this topic, you should be able to:
A bar chart is a diagram that uses rectangular bars to display data. The height of each bar shows how often something occurs — this is called the frequency (how many times something appears).
Bar charts are used for discrete data — data you can count, like the number of goals scored, shoe sizes, or favourite colours.
A class recorded their favourite fruit. The results were:
| Fruit | Frequency |
|---|---|
| Apple | 8 |
| Banana | 5 |
| Orange | 10 |
| Mango | 3 |
To draw this bar chart: draw the frequency axis going up to at least 10, label each bar with the fruit name, and make sure there are gaps between bars. The tallest bar (Orange, height 10) represents the mode — the most common value.
A dual bar chart compares two sets of data at the same time. Instead of one bar per category, you draw two bars side by side for each category — one for each group.
Key features:
Example: A teacher recorded the number of pets owned by Year 7 and Year 8 students:
| Number of Pets | Year 7 | Year 8 |
|---|---|---|
| 0 | 3 | 4 |
| 1 | 7 | 8 |
| 2 | 5 | 4 |
| 3 | 2 | 3 |
For each "number of pets" value, you draw two bars side by side — one grey for Year 7, one patterned for Year 8. Include a key explaining which is which.
Reading a dual bar chart:
Example question: How many Year 8 students are there in total? Add up all Year 8 bars: 4 + 8 + 4 + 3 = 19 students
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