Bar charts and pictograms
Bar charts compare frequencies across categories — make the bars separate and equal width.
A bar chart shows how often each category appears. The categories sit along the horizontal axis, the frequency goes up the vertical axis, and each bar should be:
- the same width as the others,
- separated by small gaps,
- read off the scale carefully — count the gridlines, not the bars.
A dual bar chart puts two related sets side by side so you can compare two groups across the same categories — boys vs girls, before vs after, brand A vs brand B. Use the same scale and a clear key.
When you describe a bar chart, lead with the modal category, then mention the smallest. A sentence like "Chips were the most popular snack in both classes, with the largest difference between the classes appearing for apples," is more useful than just reading the numbers.
- Equal-width bars with small gaps for category data.
- Read frequencies off the scale, not from the bar tops.
- Use a dual bar chart and a key when comparing two groups.
- Always title the chart and label both axes with units.