Refer to Exercise 21.35. Nuts and bolts are used in the assembly of the transmission oil coolers. They are supposed to be tightened by a torque wrench to 7 foot-pounds with specification limits LSL = 6 foot-pounds and USL = 8 foot-pounds. To test the process, three nuts are tested every 3 hours. The results for the last 75 hours were recorded. Does it appear that the process is under control?

In exercise 21.35

Long Manufacturing produces heat exchangers, primarily for the automotive industry. One such product, a transmission oil cooler, is used in the cooling of bus transmissions. It is composed of a series of copper tubes that are soldered into a header. The header must have a diameter of 4.984 inches with specification limits LSL = 4.978 inches and USL = 4.990 inches. Oversized headers result in fluid mixing and possible failure of the device. For every 100 headers produced, the operations manager draws a sample of size 4. The data from the last 25 samples were recorded. What can we conclude from these data?