Healthy control charts

What to look for in your charting software

Is the control chart you are using healthy? Does it include relevant information to give insight about your process? Whether you’re in healthcare, education, or manufacturing, healthy control charts mean accurate control charts--ones that transform data into useful information.

How does one evaluate the quality of a control chart, though? When control charts are generated by software programs, it is important to know that great diversity exists among these programs. For a complete discussion of seven ingredients of all good software programs, download our free whitepaper Seven Traits of a Healthy Control Chart. This list will guide you as you evaluate the quality of your own charting software.

Two of the traits discussed below might help as you evaluate what you need in your software program to assure healthy control charts. Look, for example, for software where control limits reflect process change.

In using control charts for process improvement, one can expect to see changes in the process over time. As a process improves, control charts must be able to reflect the new reality. If the data on a chart shows a significant improvement or change, the chart should communicate this with multiple sets of control limits. For example, it might be useful to see one set of limits before the improvement, and another set of limits after the improvement. This visualization of an improving process can be a powerful way to communicate feedback to workers in the process, management, board members, and other stakeholders.

Here is the same data set shown with two sets of control charts, the second reflecting a change in the process that has generated improvement.

Another feature of software programs to look for as you monitor and improve processes is chart notation, enabling you to add notes of explanation as needed. Sometimes, a word is worth a thousand pictures. A control chart can be rendered more useful with the addition of some well-placed text, lines, and/or arrows. These chart annotations can document process changes or note important events that affect the chart. As long as one is careful not to overuse them, annotations can be an important addition to most control charts.

Software is an outstanding tool for creating control charts, but software by itself cannot improve a process. Improvement will come from the data-based decisions that are made after interpreting the charts. That’s why the software tool that is used should have the features and flexibility to make the charts easy to interpret. To learn the seven guidelines, download our free whitepaper Seven Traits of a Healthy Control Chart and you will be well on your way to selecting the best software for creating healthy control charts.

Originally published in the March 2007 edition of Quality eLine, our free monthly newletter.

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