71. The accompanying data on x
diesel oil consumption rate measured by the drain–weigh method and y
rate measured by the CI-trace method, both in g/hr, was read from a graph in the article “A New Measurement Method of Diesel Engine Oil Consumption Rate” (J. Society Auto Engr., 1985: 28–33).

a. Assuming that x and y are related by the simple linear regression model, carry out a test to decide whether it is plausible that on average the change in the rate measured by the CI-trace method is identical to the change in the rate measured by the drain–weigh method.

b. Calculate and interpret the value of the sample correlation coefficient.