Scatter Graphs and Correlation

Scatter graphs show the relationship between two variables. They are one of the most commonly tested statistics topics on all three Edexcel GCSE papers, with questions ranging from plotting points to interpreting lines of best fit.

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Key Vocabulary

Term	Definition
Scatter graph (scatter diagram)	A graph plotting pairs of data as coordinates
Correlation	The relationship between two variables
Positive correlation	As one variable increases, the other increases
Negative correlation	As one variable increases, the other decreases
No correlation	No obvious relationship between the variables
Line of best fit	A straight line that best represents the trend of the data
Interpolation	Estimating a value within the range of the data
Extrapolation	Estimating a value outside the range of the data
Outlier	A point that does not fit the general pattern

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Types of Correlation

Positive correlation: Points go from bottom-left to top-right.

• Example: Hours of revision and exam marks.
• As revision hours increase, marks tend to increase.