The more I use them, the more I'm amazed at Control Charts.
These simple, visual tools have been around for a long time. And, I've observed, those with keen numeric skills have made them more and more complex.
Yet the simple is good. And handwritten is even better for communicating the state of a process to those involved in that process.
Think about it. It is a simple graph. Time is plotted along the bottom. It can be hours/shifts/days/months. It doesn't matter what but the period needs to be appropriate for the data. Then, each period, a person places a dot to measure the parameter in that period.
The 3 horizontal lines are a mean or target level for the paramater and upper and lower control limits (UCL and LCL). Typically, these lines are placed 2 standard deviations above and below the mean.
This recognizes that there is inherent varability in a process. If the varability stays within bounds, the process is working. If a point exceeds the bounds or shows a trend within the bounds, there is un-natural variablility.
In the first case, we say the variation comes from common causes. In the second, we call is special cause. To mess with common causes is called "Tampering". To ignore special causes is called "Neglect". Don't tamper. Don't neglect.
It's that simple.
Yet, the beauty of the control chart is not the dots or the lines or the statistics. It is in the conversation the chart data provokes. The chart focuses attention on the right thing...is the process stable? If not, what causes the instability and how do we fix it so it stays stable, longer? It allows the group to avoid finger pointing and talk about issues that matter.
It happened again for me this morning. It never gets old.
If you are not using this simple tool, try it.
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