Torque and Chrome

A torque wrench used in the final assembly of cylinder?

A torque wrench used in the final assembly of cylinder heads for automobile engines has a process standard deviation of 5.0 lb-ft. The engineers have specified that a process average of 135 lb-ft is desirable. For a simple random sample of 30 nuts that were recently tightened with the torque wrench, the sample mean was 137.0 lb-ft. Construct a 95% confidence interval for the current process mean. Discuss the possibility that the torque wrench may be in need of adjustment to correct the process mean.

Public Comments

1. The torque wrench seems like pretty good shape, its calibration doesn't seem that far off. 2lb-ft isn't a lot. I'm pretty sure that a 95% confidence level means that 95 percent of the nuts would be with in 10 lb-ft plus or minus 135 lb-ft because that is 2SD out. This is why the wrench maybe in need of calibration. Plus or minus 10 lb-ft is a wide range for all 95% to fall in. The wrench would be more accurate if the SD was one or two and not five.