![]() ![]() The chart above is an example of a stable (in statistical control) process. What is this control chart telling me about my process? Is this picture telling me that everything is all right and I can relax? Is this picture telling me that something is wrong and I should get up and find out what has happened? A control chart tells you if your process is in statistical control. To effectively use control charts, one must be able to interpret the picture. "In Control" Control ChartĪ control chart represents a picture of a process over time. How do we know if only common cause variation is present or if there are also special causes of variation present? The only way to determine this is through the use of a control chart. Employees closest to the process have the responsibility for finding and removing (if possible) special causes of variation.Ī process is in statistical control if only common cause variation is present. The second type of variation is special cause variation, which is caused by things that don't normally happen in the process. There will always be common cause variation present in a process. This is usually management's responsibility. It can be reduced only by fundamentally changing the process. One is common cause variation, which is the inherent variation in the process due to the way it was designed and is managed. There are two major sources of variation (see January 2004 e-zine, available on the website). The reason for this is that there are sources of variation in all processes. You will not always get the same result each time. Processes, whether manufacturing or service in nature, are variable. The focus for this month is on interpreting control charts. Zone Tests: Setting the Zones and Zone A. ![]()
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