Regulators must keep an eye on the weights of trucks on major highways, but making trucks stop to be weighed is costly for both the regulators and the truckers. A transport department hoped to keep costs down by measuring the weights of big trucks without actually stopping the vehicles and instead using a newly developed “weight in motion” scale. To see if the new device was accurate, workers conducted a calibration test. They weighed several trucks when stopped (static weight), assuming that this weight was correct. Then they weighed the trucks again while they were moving to see how well the new scale could estimate the actual weight. Their data are given in the table:

Weight of a Truck (thousands of pounds)
Weight in Motion                   Static Weight
26.0............................................................27.9
29.9............................................................29.1
39.5............................................................38.0
25.1............................................................27.0
31.6............................................................30.3
36.2............................................................34.5
25.1............................................................27.8
31.0............................................................29.6
35.6............................................................33.1
40.2............................................................35.5

a) Make a scatterplot for these data.

b) Describe the direction, form, and strength of the plot.

c) Write a few sentences telling what the plot says about the data.

d) Find the correlation.

e) If the trucks were weighed in kilograms (1 kilogram = 2.2 pounds), how would this change the correlation?

f) Do any points deviate from the overall pattern? What does the plot say about a possible recalibration of the weight-in-motion scale?