Free tool · Visual Communication
Is This Chart Misleading? A Chart Honesty Check
A chart can mislead without a single false number. The commonest problems are a bar chart whose axis does not start at zero, which exaggerates differences; a broken or truncated axis that is not clearly marked; two vertical axes, which let the author choose scales that make unrelated series appear to move together; a period chosen to fit the story and not explained; raw counts compared across groups of different size, where rates are needed; no sign of uncertainty when the data are a small sample or a forecast; a change in how the data is counted that is not marked; 3D effects and icons sized by height, which distort areas; red and green as the only difference between categories; a title that names the topic and not the finding; and no source, date or method. To test a chart, ask whether the reader would draw a different conclusion if they saw the whole data. If so, the chart is selecting, and it should show more or say plainly what it leaves out. A challenge to someone else’s chart should ask for the data and method, redraw it fairly and state the objection precisely.
Tool · Chart Honesty Check
3 problems that could mislead and 4 weaknesses.
Could mislead
The bars (or filled area) do not start at zero, so their lengths exaggerate the differences.
Fix: Start the axis at zero. If the differences are small and matter, use a dot plot or a line, and say what the baseline is.
Could mislead
The period was chosen but the choice is not explained, which invites the suspicion of cherry-picking.
Fix: State why the period starts and ends where it does, and show a longer period if the data exists.
Could mislead
Raw counts are compared across groups of different size, so the largest group looks worst or best whatever its rate.
Fix: Show rates per head, per case or per thousand, and give the denominator.
Weakness
The data rests on a small sample or a forecast, and the chart shows no uncertainty.
Fix: State the number of cases and show a range, an interval or a note that the figures are estimates.
Weakness
No source, date or method is stated.
Fix: Add a one-line source, the date of the data and any exclusions, so that others can check it.
Weakness
Red and green are the only difference between the categories, which many readers with colour-vision deficiency cannot tell apart.
Fix: Use colours that differ in lightness, add labels or patterns, and test in greyscale.
Weakness
The title names the topic and not the finding, so the reader must work out the point.
Fix: Write the message as the title, for example ‘Late deliveries rose from 4% to 11% in two years’.
- A chart can mislead without any false number. Honesty is a matter of the baseline, the denominator, the period, the labels and what is left out.
- Ask of every chart: would the reader draw a different conclusion if they saw the whole data? If so, show more of it.
A chart can mislead without a single false number: through where the axis starts, which period is shown, whether counts are compared without rates, and what is left out. Describe the chart you have drawn or been shown (the starting answers describe an invented, poorly drawn bar chart), and the tool lists what could mislead the reader and what is merely weak, with a fix for each. It checks the features you describe, not the chart itself. Runs in your browser; nothing is stored or sent.
How to use it
- Choose the type of chart.
- Tick the features that describe the chart: the axis, the period, counts or rates, uncertainty, source, colour, effects and title.
- Read the list of what could mislead and the weaknesses.
- Apply the fixes and tick again until the list is short.
Common questions
Must every chart start at zero?
Bar charts, whose lengths show the values, must. A line chart shows change and may start above zero, but the range should be stated and fair to the size of the change.
Why are dual-axis charts a problem?
By choosing the two scales, an author can make almost any two series appear to move together or apart. Use two charts with a shared time axis, or index both series to 100.
Can the tool look at my chart?
No. It works from the features you describe. It will not find a problem that you do not tick, so look at the chart as a stranger would.
Learn the law behind the tool
This tool is part of our Visual Communication course, with lectures, concept maps, flashcards, interactive exercises and a capstone case. Visual Storytelling for Lawyers: Drawing Honest Charts.
More free law tools
General information, simplified, mainly on American law, not legal advice. States and countries differ, and real cases turn on facts that a tool cannot capture.