problem: The specification for a plastic handle calls for length of 6.0 inches ± 0.5 inches (5.5 to 6.5 inches). The method is known to operate at a mean thickness of around 6.1 inches. The minimum acceptable method capability is 2.0. The standard deviation (σ) of the method is presently 0.08 inches.
a) Can the company meet up the customer’s specification needs at this time? If it can’t, describe if it is due to the drifting of the mean or too much variability.
b) Assume that the mean of the method has now shifted to the 5.95 inches. Determine the maximum standard deviation (σ) of this method if the company wants to make sure that it can maintain a Cpk of 2.0?
c) The specification limits haven’t changed. Assume that the mean of the method has now shifted to 5.9 inches with a standard deviation (σ) of 0.09. Describe the range (upper and lower limits) on the mean of the process to maintain the Cpk of 2.0 or more?