Statistical Process Control
Acronym
SPC
Also Known As
Control Chart
Run Chart
Examples
Taveras M. Increasing charge capture using scheduling techniques for a hospital-based ancillary service. 17th Annual Society for Health Systems Management Engineering Forum; 2005; Dallas, TX; 2005.
McCray M. How to get paid for the services you provide. 2007 Society for Health Systems Conference; 2007; New Orleans, LA; 2007.
Holst T. Improving first-case OR start times by utilizing six sigma methodologies. 2007 Society for Health Systems Conference; 2007; New Orleans, LA; 2007.
Carey R, Lloyd R. Control chart case studies. Measuring quality improvement in healthcare: a guide to statistical process control applications. New York: Quality Resources; 1995. p. 79-149.
Carey R. Improving healthcare with control charts: basic and advanced SPC methods and case studies. Milwaukee, WI: ASQ Quality Press; 2003.
Description
Statistical process control (SPC) involves the creation of control charts that are used to evaluate how processes change over time. Control charts use historical data to evaluate whether current data indicate process variation is in control (consistent) or out of control (unpredictable).
Uses
To analyze process variation.
To determine baseline performance.
When evaluating the stability of a process.
For monitoring ongoing processes.
How do I use this tool?
1. DETERMINE THE PROCESS to be analyzed.
2. DETERMINE WHAT DATA is to be collected. The data is usually directly related to a characteristic of the process in which there is concern over too much variation.
3. DETERMINE THE TIME PERIOD to collect the data and who should collect it.
4. COLLECT AT LEAST 25 DATA POINTS. Record when each point was collected and arrange them in order.
5. DETERMINE THE SCALE for the y-axis based on the data collected and label it. The scale should be about 1.5 times the range (maximum data point minus minimum data point) of the collected data.
6. DRAW THE HORIZONTAL AXIS, label it, and mark the unit of time.
7. PLOT THE DATA POINTS.
8. INTERPRET THE RUN CHART:
a. Eight points in a row above or below the center line indicates a process shift.
b. Six consecutive increasing or decreasing points indicates a trend.
c. Fourteen consecutive points alternating up and down indicates the process is cyclical.
Expertise Required
Users of this tool usually have some training or experience in its use.
Recommended Supplies/Materials
Data
Statistical or graphing software
Advantages
Data trends become clear.
Easy to see when points are out of control, inconsistent, or varied.
Disadvantages
Value of the method is dependent on the analysts' skill.
Requires statistical knowledge and understanding.
Where can I go to learn more?
Lighter D. Statistical process control: Basic principles. In: Moore C, editor. Quality management in health care: principles and methods. 2nd ed. Sudbury, MA: Jones and Bartlett Publishers; 2004. p. 103-23.
Carey R, Lloyd R. Measuring quality improvment in healthcare: a guide to statistical process control applications. New York: Quality Resources; 1995.
University Research Co. LLC. Health care improvement project: run and control charts. 2008 [cited 2009 July 28];
American Society for Quality. Data collection and analysis tools: Control chart. 2009 [cited 2009 June 26]; Available from: http://www.asq.org/learn-about-quality/data-collection-analysis-tools/overview/control-chart.html