Statistical Process Control Charts
Statistical Process Control Charts
Statistical Process Control Charts
How to tell whether a shift, trend, or pattern is occurring:
• Shifts: If eight or more consecutive points fall on one side of the center line, it indicates a special cause may have influenced the process. Points on the average line don’t count. When special causes are detected, the team needs to work to find the cause and eliminate it from the process.
• Trends: Six consecutive jumps in the same direction indicate that a special cause may be acting on the process to cause a trend when there are 9 to 20 data points on the chart. Five or more ascending or descending points are needed to indicate a special cause when you have 5 to 8 points on the chart and 7 or more consecutive ascending or descending points are necessary when you have 21 to 100 data points on the chart. Flat line segments are not included.
• Pattern: If you see a pattern that recurs eight or more times in a row, it is recommended
that you look for a special cause. When only common cause variation is found, the team should start a quality improvement process.
Case Scenario: The chief surgeon comes storming in to the quality and safety meeting waving a piece of paper. “Just look at these data! Our process is “completely out of control!” For the Discussion this week, consider the accuracy of the surgeon’s statement by answering the questions based on the following run chart:
1. Is the process depicted out of control? Why or why not?
2. Are there common causes, special causes, or trends evident in the data?
3. What other data should be considered when making a decision?
4. Based on your analysis of these data, what should the team be doing to change the process?
5. Why is run charting particularly important to measurement of nursing sensitive outcomes of care?
