Teaching article
A bar graph's scale changes how height should be read
Use equal numerical steps and label what the heights or lengths represent.
Cover the category labels briefly and inspect the vertical scale. Readers need the baseline and interval sizes before interpreting a bar's value; the tallest shape alone tells only part of the story.
Check the baseline and interval spacing before comparing bar heights. The visual difference needs to be interpreted using the actual scale.
Check the intervals before comparing bars
Counts of three and six should not be shown with equal-height bars when the same scale is used.
Choose a suitable shared scale. Draw bars from a common baseline. Check each bar against its count.
Visual decoration should not obscure the baseline or scale. Can another reader recover the original count?
Provide pre-labelled axes.
Resources
- Reflection Journal Template — Use the blank reflection space for observations; write the measurement units and setup separately.
Further reading
Read next
- Ask a graph a question its data can answer
- Map directions work better with a shared viewpoint
- Three items at one price: make the receipt line explicit
Explore Money, measurement and data. Browse all teaching articles.