Scatter graphs: GCSE Maths revision
Scatter graphs show two variables. Correlation can be positive, negative or none. A line of best fit should follow the trend, with points roughly balanced either side. Do not extend it blindly (interpolation vs extrapolation).
Correlation is not causation
A strong pattern does not prove one variable causes the other. Exam comments want that sentence when the context is real-world.
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
As x increases, y decreases. What correlation is that?
Why might a line of best fit be unreliable for a value far outside the data?
Common mistakes
- Forcing the line through the origin.
- Joining the dots instead of a straight trend line.
Answers and working
Frequently asked questions
Does the line have to go through every point?
No. It is a trend, not a join-the-dots graph.
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