Monitoring surgery complications. 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?
Month | Complications | Procedures Sampled |
1 | 14 | 105 |
2 | 12 | 97 |
3 | 10 | 115 |
4 | 12 | 100 |
5 | 9 | 95 |
6 | 7 | 111 |
7 | 9 | 68 |
8 | 11 | 47 |
9 | 9 | 83 |
10 | 12 | 108 |
11 | 10 | 115 |
12 | 7 | 94 |
13 | 12 | 107 |
14 | 9 | 99 |
15 | 15 | 105 |
16 | 13 | no |
17 | 7 | 97 |
18 | 10 | 105 |
19 | 8 | 71 |
20 | 5 | 48 |
21 | 12 | 95 |
22 | 9 | 110 |
23 | 7 | 103 |
24 | 9 | 95 |
25 | 15 | 105 |
26 | 12 | 100 |
27 | 8 | 116 |
28 | 2 | 110 |
29 | 9 | 105 |
30 | 10 | 120 |
Totals | 294 | 2,939 |
c. Find the value of
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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