A manufacturer of ballpoint pens randomly samples 400 pens per day and tests each to see whether the ink flow is acceptable. The proportions of pens judged defective each day over a 40-day period are listed in Table 7.7. Construct a control chart for the proportion p defective in samples of n = 400 pens selected from the process.

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Proportions of Defectives in Samples of n = 400 Pens Day Proportion Day Proportion Day Proportion Day Proportion -23456969 1 0.0200 11 0.0100 0.0125 12 0.0175 22 21 0.0300 31 0.0225 22 0.0200 32 0.0175 0.0225 13 0.0250 23 0.0125 33 0.0225 0.0100 14 0.0175 24 0.0175 34 0.0100 0.0150 15 0.0275 25 0.0225 35 0.0125 0.0200 16 0.0200 26 0.0150 36 0.0300 7 0.0275 17 0.0225 27 0.0200 37 0.0200 8 0.0175 18 0.0100 28 0.0250 38 0.0150 0.0200 19 0.0175 29 0.0150 39 0.0150 10 0.0250 28 20 0.0200 30 0.0175 40 0.0225