Defective micron chips. A manufacturer produces micronchips for personal computers. From past experience, the production manager believes that 1% of the chips are defective. The company collected a sample of the first 1,000 chips manufactured after 4:00 PM. every other day for a month. The chips were analyzed for defects, then these data and MINITAB were used to construct the p-chart shown on p. 824.
a. Calculate the chart's upper and lower control limits.
b. What does the p-chart suggest about the presence of special causes during the time when the data were collected?
c. Critique the rational subgrouping strategy used by the disk manufacturer.