Attribute Control Charts

  

  1. A hospital is      analyzing nosocomial infections and wants to reduce their infection rate      below the national average of 2.0%. They have sampled 40 cases every week      for the last 20 weeks. The data are shown below. Create p and np control      charts. Interpret the graphs. How is the hospital performing in relation      to its stated goal?
  2. Walter      Shewhart ([1931] 1980) presented the following data in his classic      Economic Control of Quality of Manufactured Product. Create a p chart for      each machine. Does either of the two machines show evidence of special      cause variation?
  3. From January      1846 through December 1848 Semmelweis ([1860] 1983) recorded births and      the number that resulted in the death of the mother at his hospital. The      data is available in the Chapter07.xls file, in the Problem07–03 tab.      Create a p chart to analyze performance. Interpret the chart. Was the      system stable? 
  4. Postsurgical      infections have been reported to affect 2% to 5% of the 16 million      patients who undergo surgery in U.S. hospitals. Infections increase the      chance of complications and death. Antibiotics given one hour prior to      surgery have been shown to reduce the probability of infection. The      director of quality improvement has sampled 20 patients per week over the      preceding 25 weeks. The data is available in the Chapter07.xls file in the      Problem07–04 tab. The data collected records whether a patient contracted      an infection after surgery. Create a p chart to analyze performance.      Interpret the hospital’s performance based on your control chart and      identify any issues that should be investigated. Assuming the aver- age      rate of infection is 3.5%, is the hospital doing a good job?
  5. Readmission      rates within one year for congestive heart failure have been documented at      35%. A local heart program wants to assess its performance against this      standard. The pro- gram has randomly selected ten patients per month over      a 24-month period for review. The data is available in the Chapter07.xls      file, in the Problem07–05 tab. Some of the patients were deleted from the      sample due to death, relocation, or other reasons that preclude follow-up.      Create a p chart. Is the process stable? How is the program performing      relative to the documented standard? Since not all months have 10      observations, either use 10 as the sample size or use the average sample      size to calculate the control limits.
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