Charts can mislead — Media, 7–10 years
Charts turn numbers into pictures, which can make patterns easier to see. But the scale, labels and chosen data can make a small difference look huge or hide an important change.
A chart is a picture of numbers
A chart uses positions, lengths, colours or symbols to show numbers. This lets us compare things quickly, but the picture is built from choices. To read it fairly, check what is being counted, what each mark means and where the scale begins.
Why charts need careful reading
People made charts to share many measurements more clearly than a long list of numbers. The problem is that a chart can look convincing before we inspect its scale. A shortened vertical scale, missing time points or a selective choice of data can change the impression without changing the numbers themselves.
One difference, two pictures
A class poll gives 42 votes for apples and 45 for bananas: a difference of 3 votes. On a bar chart from 0 to 50, the bars look almost equal. If the chart starts at 40, the visible bars are 2 and 5 units high, so bananas look much more popular. The numbers stayed the same; the scale changed the picture.
The tallest bar wins
We often trust our eyes and compare the visible heights first. That is reasonable because charts are designed to make comparisons quick. But a tall-looking bar may only show a small difference if the scale starts above zero, so read the numbers and scale before deciding.
Charts outside school
Charts appear in weather apps, sports results, travel information, news reports and reports about energy or money. They help you compare rainfall, points, prices or time. You do not need to distrust every chart; you need to check its labels, scale and source before using its message.
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