A council records the age x x\,x years and annual repair cost y y\,y pounds for a self-contained random sample of 40 buses. The regression line of y y\,y on x x\,x is y=315x+740y=315x+740y=315x+740. One bus is 8 years old and has an annual repair cost of £3900.
Find the predicted repair cost for this bus.
Find its residual.
Explain why the regression line alone cannot establish that age causes higher repair costs.
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.