1. DVD production. Plastic covers for DVDs must be man- ufactured with enough precision so that a DVD can prop- erly fit into the cover. Specifically, the diameter of the central plastic piece over which the DVD is placed must not vary more than a certain amount. A manufacturer has been producing DVD covers for several months and has had no complaints from its customers. It decides to use the past 2 months of data to estimate the mean and standard deviation of the process. Are the limits for quality monitor- ing based on these quantities control or specification lim- its? Explain.
2. Roulette. An observer at the roulette wheel in Monte Carlo notices that there seems to be no pattern to the num- bers that come up during an entire evening. Is this an ex- ample of special- or common-cause variation? Explain.