Question: Making auto parts A grinding machine in an auto parts plant prepares axles with a target diameter μ = 40.125 millimeters (mm). The machine has some variability, so the standard deviation of the diameters is σ = 0.002 mm. The machine operator inspects a random sample of 4 axles each hour for quality control purposes and records the sample mean diameter x¯. Assuming that the process is working properly, what are the mean and standard deviation of the sampling distribution of x¯? Explain.