A process that produces titanium forgings for automobile turbocharger wheels is to be controlled through the use of a fraction nonconforming chart. Initially, one sample of size 150 is taken each day for 20 days, and the results shown in Table 6E.4 are observed.

a. Establish a control chart to monitor future production.
b. What is the smallest sample size that could be used for this process and still give a positive lower control limit on the chart?

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Nonconforming Units Nonconforming audi Dy Units Dav 12 13 14 15 16 17 18 19 20 10