Misleading graphs — Data, 14–17 years
A graph can display true numbers and still create a false impression through its scale, labels or design.
How a graph can mislead
A graph is a visual argument: its scale and shape guide what you notice first. If the vertical axis starts at 95 instead of 0, a rise from 98 to 100 can look enormous, although it is only a small change. Accurate data do not guarantee an honest impression.
Why this matters
People use graphs to compare results quickly, so a visual exaggeration can affect choices about money, health or public policy. The problem arose because readers cannot inspect every number equally closely. Learning to check scales and labels protects you from persuasive pictures that hide the size of a change.
A worked example
A shop reports sales rising from 100 to 110 items. First, find the absolute change: 110 − 100 = 10 items. Second, find the relative change: 10 ÷ 100 = 0.10, or 10%. Third, compare graphs: an axis from 0 shows a modest rise; an axis from 99 makes the bars look ten times taller.
The trap: judging the picture only
A common mistake is to say that the longest bar represents the biggest amount without reading the axis or units. That feels natural because bar length usually carries the comparison. But a broken axis, unequal intervals or missing units can change the story, so inspect the scale before interpreting the shape.
Where it is used
News reports, adverts and social-media posts often compress data into one striking chart. Before sharing or believing it, read both axes, check the units, look for a truncated scale and compare the actual numbers. This does not mean every unusual graph is dishonest; it means the design deserves checking.
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