Statistics · Scatter graphs & correlation
Chapter 1 · 3
The idea
Predicting from a line of best fit
How to read an estimate off a line of best fit in both directions, why a prediction inside the data is trustworthy and one outside it is not, and what the gradient of the line means in the context of the question.
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Statistics · Scatter graphs & correlation
Predicting from a line of best fit
How to read an estimate off a line of best fit in both directions, why a prediction inside the data is trustworthy and one outside it is not, and what the gradient of the line means in the context of the question.
Why it works
A machine for making predictions
Once a scatter graph has a line of best fit, the line stops being decoration and becomes a machine for making predictions. Feed it a value on one axis and it hands one back on the other. That is what "use your line of best fit to estimate…" asks, and it runs in both directions: to get from , go up from to the line, then across to the -axis; to get from , go across from to the line, then down. The second catches people out — the instinct is to start on the horizontal axis.Keep reading — free
The rest of the explanation, plus 3 worked examples you step through move by move.
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