A regression line for monthly electricity cost c c\,c pounds on average temperature t ∘Ct\,^{\circ}\mathrm Ct∘C is c=94.6−2.85tc=94.6-2.85tc=94.6−2.85t, based on winter temperatures from 1 ∘C1\,^{\circ}\mathrm C1∘C to 11 ∘C11\,^{\circ}\mathrm C11∘C.
Interpret the gradient.
Estimate the cost when t=8t=8t=8.
Explain why the line should not be used without caution at t=25t=25t=25.
278 exam-style questions on CCEA A Level Maths 2.5 Data presentation and interpretation, covering 2.5.1 Data presentation and interpretation, 2.5.2 Data presentation and interpretation, 2.5.3 Data presentation and interpretation, 2.5.4 Data presentation and interpretation, 2.5.5 Data presentation and interpretation, 2.5.6 Data presentation and interpretation, 2.5.7 Data presentation and interpretation, 2.5.8 Data presentation and interpretation, 2.5.9 Data presentation and interpretation, and 2.5 Data presentation and interpretation. Each one has a worked solution and a mark scheme showing where the marks go.