Statistics · Scatter graphs & correlation
Chapter 1 · 3
The idea
Scatter graphs & correlation
Why one point on a scatter graph is one individual measured twice, how to describe correlation by type and strength in the words of the question, why a correlation never proves a cause, and how to place a line of best fit — through the bulk of the data, balanced either side, ignoring a genuine outlier.
A full journey — read it, play with it, work it, then earn real exam marks. Everything stays on the timeline below.
In this lesson — start anywhere
Statistics · Scatter graphs & correlation
Scatter graphs & correlation
Why one point on a scatter graph is one individual measured twice, how to describe correlation by type and strength in the words of the question, why a correlation never proves a cause, and how to place a line of best fit — through the bulk of the data, balanced either side, ignoring a genuine outlier.
Why it works
One individual, measured twice
Almost every graph you have met so far plots one quantity. A scatter graph plots two measurements of the same individual at once, and that is the whole idea. Take ten students and record two numbers for each of them: the hours they revised and the mark they scored. Student four revised for hours and scored , so student four is the single point . Ten students, ten points, and nothing else on the graph.Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
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