An article on the use of control charts for monitoring the proportion of post operative complications at a large hospital was published in the International Journal for Quality in Health Care (October 2010). A random sample of surgical procedures was selected each month for 30 consecutive months, and the number of procedures with postoperative complications was recorded. The data are listed in the accompanying table.

a. Identify the attribute of interest to the hospital.
b. What are the rational subgroups for this study?
c. Find the value of p for use in a p-chart.
d. Compute the proportion of post-op complications in each month.
e. Compute the critical boundaries for the p-chart (i.e., UCL, LCL, Upper A-B boundary, etc.).
f. Construct a p-chart for the data.
g. Interpret the chart. Does the process appear to be in control? Explain.

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Procedures Month Complications Sampled 14 12 10 12 105 97 115 3 4 100 95 6. 11 83 108 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 12 10 115 94 12 15 105 110 97 105 13 10 5 12 95 110 103 95 105 100 116 110 105 120 15 12 8. 2 9. 10 Totals 294 2,939