Refer to the Plastic Packaging case in. The ideal lip width is 1.5 in. The lip width data in Table 3.21 (in inches) were taken on the same bags represented in.
(a) Is this a variables data or an attributes data scenario? Why?
(b) Find the subgroup means, ranges, and standard deviations.
(c) Make retrospective control charts for lip width variability and lip width mean based on the sample ranges.
(d) In view of the appearance of your chart for variability of lip width, does it make sense to seriously examine the chart for mean lip width? Why or why not?
(e) Instead of making the completely retrospective charts asked for in (c), is it possible to incorporate some "standards" information and make a different chart for mean lip width? Explain.
(f) Instead of treating all 18 samples at once as in part (c), for each day separately, make retrospective R and x charts. What are your conclusions regarding process stability for each day separately?
(g) Find three daily estimated lip width standard deviations. How do these estimates compare to that calculated when the complete set of data is used?
(h) Would there be advantages to using subgroup standard deviations instead of subgroup ranges in parts (c) and (f) above? Explain.