Question

How does the fuel consumption of a car change as its speed increases? Here are data for a 2014 Chevrolet Cruze Turbo Diesel. Speed is measured in miles per hour, and fuel consumption is measured in miles per gallon.

Speed 10 20 30 40 50 60 70 80

Fuel 38.1 54.0 68.4 63.6 60.5 55.4 50.6 43.8

a. Make a scatterplot. (Which is the explanatory variable?)

b.Describe the form of the relationship. It is not linear. Explain why the form of the relationship makes sense.

c.It does not make sense to describe the variables as either positively associated or negatively associated. Why?

d. Is the relationship reasonably strong or quite weak? Explain your answer.

Answer 1

A)

SPEED IS explanatory variable

b)

graph is not linear.because relationship is curved

As the speed of the car increases, the fuel consumed first increases and decreases again after reaching the highest point possible.

A car doesn’t reach higher speeds by consuming more fuel. In other words, car speeds are not influenced by fuel consumption.

c)

There is no particular association between the variables at all, so it is certainly neither positive nor negative.

d)

The relationship is quite weak — any simple curve drawn would be such that there is wide scatter around it, so that curve would not be very useful for prediction