Statistics & Probability is a core part of GCSE Maths. Revise the key concepts and common mistakes below, then lock them in with the free games.
Key concepts
MeanAdd all values, divide by how many there are
MedianMiddle value once data is sorted in order
ModeValue that appears most often in the data
RangeLargest value minus smallest value
Discrete dataCounts only certain values, like number of pets
Continuous dataCan take any value, like height or time
IQRUpper quartile minus lower quartile — middle 50% spread
Box plotDiagram showing min, Q1, median, Q3, max
CorrelationHow two variables change together on a scatter graph
Line of best fitStraight line drawn through the trend of points
InterpolationReading within the range of the data — reliable
ExtrapolationReading outside the data range — unreliable
FrequencyHow many times a value or class appears
Modal classGrouped class with the highest frequency
Common mistakes to avoid
Questions where students often pick the tempting wrong answer — make sure you know the right one:
Which average is best to use for the data set [2, 3, 3, 4, 4, 4, 5, 100]?✗ The mean — it always gives the most accurate average. ✓ The median (3.5) — it isn't distorted by the outlier 100, unlike the mean.
What is the range of the data set [4, 7, 2, 9, 5]?✗ From 2 to 9 — the range is given as two values. ✓ 7 — the largest minus the smallest (9 - 2).
If a data set has an extreme outlier, which average is most affected?✗ The median is most affected because the outlier shifts the middle. ✓ The mean — because every value (including the outlier) contributes to it.
Which of these is CONTINUOUS data?✗ Number of pets owned ✓ Height of a tree
On a box plot, what does the IQR measure?✗ Total range of data ✓ Spread of the middle 50%
Practise Statistics & Probability — free games
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