At a Large Automobile Factory,four Different Machines Are Used to Produce

Multiple Choice

At a large automobile factory,four different machines are used to produce disc brakes.To make sure that the disc brakes are all being produced with comparable diameters,daily samples of 16 disc brakes are taken from the production lines of each of the four machines and their diameters measured.The deviation from the goal diameter of 322 micrometers is measured to the nearest micrometer.Assume that the distribution of these deviations is approximately Normal with a common standard deviation.Does it appear that disc brakes made on the four machines are made with equal mean diameters? SPSS output is included below. Some summary measures for the four machines are given below. Suppose we are interested in the contrast that compares the average of machines 1,3,and 4 (the most recently purchased machines) to machine 2 (a slightly older model) .

What is a 95% confidence interval for the contrast ?

A) (-33.41,-0.29)
B) (-22.61,-11.09)
C) (5.91,17.43)
D) (12.04,21.66)