Which Graph Should I Use? Bar, Line, Scatter and Line Plot Compared

Students often pick a graph by habit. Choosing deliberately is a skill, and it makes results much clearer.

Choose by the question

If you want to…	Use a…	Example
Compare amounts across categories	Bar graph	Meltwater for salt, sugar, sand and nothing
Show how something changes over time	Line graph	Temperature of a cup every 5 minutes
Show the relationship between two measurements	Scatter plot	Height versus hand span
Show how a set of single numbers is spread	Line plot	Class guesses for one minute
Show parts of a whole	Pie chart	How a day’s garbage splits into landfill, recycling, compost

Quick rules for good graphs

Title that says what it shows.
Axis labels with units (seconds, cm, °C).
An even scale. Equal spaces mean equal amounts.
Start the axis at zero for bar graphs, or tell readers if it doesn’t.
Label what matters, and remove clutter.
Don’t join the points on a scatter plot. Draw a trend line.

Sneaky tricks to watch for

Graphs can mislead without lying. Check for:

A cut-off axis. Starting a bar graph at 90 instead of 0 makes small differences look huge.
Stretched or squashed scales. The same data looks flat or dramatic.
Missing labels or units.
Cherry-picked time spans. Showing only the good part.
3D effects that distort sizes.

A good exercise: give students the same numbers drawn two ways, one honest and one built to exaggerate, and ask which they’d trust.

Which graph for experiment data?

Most fair tests with a few conditions suit a bar graph of averages. Measurements over time suit a line graph. If you changed a number (such as ramp height) and measured another, a scatter plot or line graph shows the relationship.

Tools

You can make graphs on paper, or with our free graph maker.

See Which graph tells the truth? for a full lesson on honest and misleading graphs, and How fast are our reaction times? for data to graph. Sign up for three lessons free.