Control ChartControl chart as a tool is little complex to construct. It requires some mathematical calculations to construct. But when constructed properly it is very easy to understand and use. Control chart basically represents the variation in a process. It keeps track of these changes against predefined upper and lower control limits. These limits are defined according to the requirements of the process. Studies show that changes are significant, when the changes exceeds three times of the standard deviation. Therefore this can be used as a rough guideline in constructing the chart. You can see a sample control chart below
When you construct the chart, if you have already eliminated the main causes for the problems you are tracking, the variation should be random. If it is biased then this shows some cause for the problem which is unsolved. For an example if you are plotting the number of defects and if the chart has a continuous increment, this suggest that something is going wrong continuously in your system. Control chats perform well because they are based on figures. These details are plotted against references. Therefore anyone can see where the process is at that moment. |
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