A grinding machine in an auto parts plant prepares axles with a target diameter of 40.125 mm. The machine has some variabilities, so the standard deviation of the diameter is 0.002 mm. The machine operator inspects a random sample of four axles each hour for quality control purposes and records the same diameter x. Assume the machine is working properly. Identify the meaning of the sampling distribution of x.
a. Distribution of axle diameters in the population
b. Distribution of sample means of axle diameters
c. Distribution of machine variabilities
d. Distribution of individual axle measurements
