Watch out
Treating a prediction as exact.
Scottish National 5 Mathematics
National 5 Maths Scattergraphs and linear models
Form and use a best-fitting straight-line model from scattergraph data.
Formula reference
Check the National 5 rules and formulae linked to this topic.
Which method?
Match exam clues to a suitable method.
Before you start
- Choose two clear points on the fitted line, not necessarily data points.
- Store the fitted gradient and intercept before substituting, and report a model prediction as an estimate.
- Read the command word, record the units or requested form, and make the final answer match it.
Explanation
Scattergraphs and linear models is an assessed part of Scottish National 5 Mathematics in the statistics area. Form and use a best-fitting straight-line model from scattergraph data.
Choose two clear points on the fitted line, not necessarily data points.
Find the gradient and intercept to form the model.
Substitute the given x-value and describe the result as an estimate.
The interactive bank below mixes direct skills, reverse questions, interpretation and contextual reasoning rather than repeating one number pattern.
Visual support
Scatter graph trend
Key formulae and rules
- Use y = mx + c as the best-fitting straight-line model.
Check
Check the calculation, then state what the result means for the named data or model rather than treating an estimate as exact.
Exam tip
Quote the relevant statistic or model value, then interpret it in the context of the named data.
Calculator tip
Store the fitted gradient and intercept before substituting, and report a model prediction as an estimate.
Worked examples
Worked example 1
Scattergraphs and linear models worked example
A fitted model is y = 2.4x + 7. Estimate y when x = 15.
- Substitute x = 15
- y = 2.4(15) + 7 = 43
Answer: Estimated y = 43
Watch out
- Treating a prediction as exact.
- Using a single data point as the line equation.