Consider again the plastic packaging case of problem 9. (a) Who is the immediate customer of the hole-punching process? (b) Is it possible for the hole-punching process to produce hole locations with small variation and yet still produce a poor-quality bag? Why or why not? (c) After observing that 100 out of 100 sampled bags fit over the two 6- in wickets, an analyst might conclude that the hole-punching process needs no improvement. Is this thinking correct? Why or why not? (d) Hsiao, Linse, and McKay used statistical methodologies consistent with steps 1, 2, 3, and 4 of the six-step process-oriented quality assurance cycle and detected unacceptable variation in hole location. Would it be advisable to pursue step 6 in Table 1.1 in an attempt to improve the hole-punching process? Why or why not?
Problem 9
Plastic Packaging. Hsiao, Linse, and McKay investigated the production of some plastic bags, specifically hole positions on the bags. Production of these bags is done on a model 308 poly bag machine using preprinted, prefolded plastic film delivered on a roll. The plastic film is drawn through a series of rollers to punches that make holes in the bag lips. An electronic eye scans the film after it is punched and triggers heated sills which form the seals on the bags. A conveyor transports the bags to a machine operator who counts and puts them onto wickets (by placing the holes of the bags over 6- in. metal rods) and then places them in boxes. Discuss how this process and its output might variously fall into the cells 1, 2, 3, or 4 in problem 8.
Problem 8
The following matrix (suggested by Dr. Brian Joiner) can be used to classify production outcomes. Good result of productin means there is a large proportion of product meeting engineering specifications. (Bad result of production means there is a low proportion of product meeting requirements.) Good method of production means that quality variables are consistently near their targets. (Bad method of production means there is considerable variability about
