Question

A taxi company monitoring the safety of its cabs kept track of the number of miles tires had been driven (in thousands) and the depth of the tread remaining (in mm). Their data are displayed in the scatter plot. They found the correlation to be r = – .86 and the equation of the regression line to be tread=36-0.6(miles).

1. Use the equation to predict the tread for a car driven 25 thousand miles.

2. Use the equation to predict the tread for a car driven 45 thousand miles.

3. Describe the association in the scatter plot. Was it appropriate to find a regression equation?

4. Explain what the slope of the equation means in context.  

5. After being driven 45 thousand miles, a tire’s tread measured 6.3mm. What is the residual for this data point? In general, what does a negative residual mean in this context?

Answer 1