The Minnesota Department of Transportation installed a state-of-the-art weigh-in-motion scale in the concrete surface of the eastbound lanes of Interstate 494 in Bloomington, Minnesota. After installation, a study was undertaken to determine whether the scale's readings correspond with the static weights of the vehicles being monitored. (Studies of this type are known as calibration studies.) After some preliminary comparisons using a two-axle, six-tire truck carrying different loads (see the table on p. 551), calibration adjustments were made in the software of the weigh-in-motion system and the scales were reevaluated.

a. Construct two scattergrams, one of y, versus x and the other of y, versus x.

b. Use the scattergrams of part a to evaluate the performance of the weigh-in-motion scale both before and after the calibration adjustment.

c. Calculate the correlation coefficient for both sets of data and interpret their values. Explain how these correlation coefficients can be used to evaluate the weigh-in-motion scale.

d. Suppose the sample correlation coefficient for y, and x was 1. Could this happen if the static weights and the weigh-in-motion readings disagreed? Explain.