SPC/Statistics > Run Charts

The run chart is not considered a Shewart control chart and it is the least powerful of all the charts. This chart does, however, have a place. In many cases it is a good idea to start out by charting a process with this tool before applying a more powerful control chart. It will allow the user to remove inconsistencies that occur over time. A control chart might obscure some important information by averaging it out. The pre-control chart uses a technique known as "Stop Light Gaging" or "Zone Pre-Control". The zones are color coded as follows:

• The green zone prompts the user to continue the run (within tolerance state) with the acceptable observations that fall within this region.
• The yellow zone prompts the operator to use caution (near out of tolerance state) and look for possible problem causes.
• The red zone prompts the operator to stop the run (out of tolerance state) and determine the cause before starting the process again.