A manufacturing company uses a certain type of steel rod in one of its products. The design

Question:

A manufacturing company uses a certain type of steel rod in one of its products. The design specifications for this rod indicate that it must be between 0.353 to 0.357 inches in diameter. The machine that manufactures these rods is set up to produce them at 0.355 inches in diameter, but there is some variation in its output. Provided that the machine is producing rods within 0.353 to 0.357 inches in diameter, its output is considered acceptable or within control limits. Management uses a control chart to track the diameter of the rods being produced by the machine over time so that remedial measures can be taken if the machine begins to produce unacceptable rods. Figure shows an example of this type of chart.
Unacceptable rods represent waste. Thus, management wants to develop a procedure to predict when the machine will start producing rods that are outside the control limits, so it can take action to prevent the production of rods that must be scrapped. Of the time series models discussed in this chapter, which is the most appropriate tool for this problem? Explain youranswer.