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Comparing two data sets is an exam staple. The rule is simple: compare a measure of location and a measure of spread, then interpret both in the context of the question.
What you'll be able to do
A good comparison always covers things: a measure of (which set is higher on average) and a measure of (which set is more consistent). One without the other is incomplete.
Use the measures for both sets. If the data has outliers, use the median and IQR (robust); if it is roughly symmetric with no outliers, the mean and standard deviation are fine — but be consistent across both sets.
Tip — Outliers → median & IQR. Symmetric, clean data → mean & standard deviation. Never mix measures across the two sets.
Always phrase conclusions using the situation. “The mean mark for Class A (62) is higher than Class B (55), so A performed better on average; A’s smaller standard deviation means its marks were more consistent.”
Formula recap
Common mistakes to avoid
Key takeaways
Test yourself
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Real past-paper questions on Comparing Data, marked mark-by-mark. How you do feeds straight into your weak-topic list, so your revision keeps targeting what actually needs work.
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