Who invented control chart?
Walter A. Shewhart
Invented by Walter A. Shewhart while he was working for Bell Labs in the ’20s, control charts have been used in a variety of industries as part of a process improvement methodology.
What are the control charts used for?
Control charts are used to routinely monitor quality. Depending on the number of process characteristics to be monitored, there are two basic types of control charts. The first, referred to as a univariate control chart, is a graphical display (chart) of one quality characteristic.
Which control chart is used for Attributed data?
The p chart for attribute data.
What are attribute control charts?
Attribute Control Charts are a set of control charts specifically designed for tracking defects (also called non-conformities). Depending on the type of Attribute Control Chart, the number of defective parts are tracked (p-chart and np-chart), or alternatively, the number of defects are tracked (u-chart, c-chart).
What is the purpose of a control chart?
One of the purposes of a control chart is to track a process to see when something has changed. You do that by “locking” the control limits once you have a stable process. This means that you extend the average and control limits into the future and monitor your process results against those values.
How to create a statistical process control chart?
Determine the appropriate time period for collecting and plotting data. Collect data, construct your chart and analyze the data. Look for “out-of-control signals” on the control chart. When one is identified, mark it on the chart and investigate the cause. Document how you investigated, what you learned, the cause and how it was corrected.
How to create a quality improvement control chart?
When determining whether your quality improvement project should aim to prevent specific problems or to make fundamental changes to the process Choose the appropriate control chart for your data. Determine the appropriate time period for collecting and plotting data. Collect data, construct your chart and analyze the data.
What does the top and bottom of a control chart mean?
The top chart monitors the average, or the centering of the distribution of data from the process. The bottom chart monitors the range, or the width of the distribution. If your data were shots in target practice, the average is where the shots are clustering, and the range is how tightly they are clustered.