Percentages make groups comparable — Data, 11–13 years
A percentage tells how large a part is when the whole is treated as 100. This makes fairer comparisons between groups of different sizes.
The same number is not always the same share
A percentage describes a part in relation to its whole. Ten pupils may be a large share of a class of 20, but a small share of a school of 500. Percentages put both situations onto the same 0-to-100 scale.
Why use percentages?
Raw counts can make a bigger group look more successful simply because it has more people. Percentages solve this by asking, “Out of every 100, how many would be in this group?” That makes rates easier to compare.
Comparing two clubs
Club A has 12 winners among 20 players: 12 ÷ 20 = 0.6, so 60%. Club B has 18 winners among 40 players: 18 ÷ 40 = 0.45, so 45%. Although B has more winners, A has the larger share.
More people does not mean a higher percentage
A common mistake is to compare only the numbers on top, such as 18 winners with 12. That feels sensible because 18 is larger, but each number comes from a different-sized group. Check the denominator—the whole group—before comparing percentages.
Rates in everyday reports
Percentages help compare attendance at two events, recycling in different neighbourhoods, or correct answers in two classes. They are useful whenever the groups have different sizes. A careful reader still checks what the 100% whole actually is.
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