57. The Turbine Oil Oxidation Test (TOST) and the Rotating Bomb Oxidation Test (RBOT) are two different procedures for evaluating the oxidation stability of steam turbine oils. The article Dependence of Oxidation Stability of SteamTurbine Oil on Base Oil Composition (J. Soc. Tribologists and Lubricat.

Engrs., Oct. 1997: 19—24) reported the accompanying observations on x  TOST time (hr) and y 

RBOT time (min) for 12 oil specimens.

TOST 4200 3600 3750 3675 4050 2770 RBOT 370 340 375 310 350 200 TOST 4870 4500 3450 2700 3750 3300 RBOT 400 375 285 225 345 285

a. Calculate and interpret the value of the sample correlation coef cient (as did the article s authors).

b. How would the value of r be affected if we had let x  RBOT time and y  TOST time?

c. How would the value of r be affected if RBOT time were expressed in hours?

d. Construct a scatter plot and normal probability plots and comment.

e. Carry out a test of hypotheses to decide whether RBOT time and TOST time are linearly related.