Control Charts vs Run Charts
Control Chart is a graphical tool used to determine process performance with time. These were developed by Walter A. Shewhart and hence are also known as Shewhart charts. These charts help determine whether the process is stable or not. If the process is stable, the process will only have inherent variation (Common Cause variation). The region of common cause variation is given by Control limits (Upper and Lower control limits). Any process variation outside these limits is considered as Special Cause Variation
Run Chart is a plot of a metric performance with respect to time. It is used to check for presence of special causes in the process or in other words to determine whether the process is random or not (as a perfectly random process will not have any special causes). A Run Chart checks for four types of special causes - Trends, Oscillations, Clusters and Mixtures.
Trends - Sustained drift in the metric performance either upwards or downwards.
Oscillations - Continuous fluctuations in the metric performance indicating that a process is not steady.
Clusters - Group of metric performance readings in one area of chart or continuous readings of metric performance within a short range.
Mixtures - Continuous crossing of the mean or the center line (in subsequent metric performance readings) usually indicating that process is operating at different levels.
An application-oriented question on the topic along with responses can be seen below. The best answer was provided by Natwar Lal on 5th September 2019.
Applause for the respondents- Mohamed Asif, Vinod Shanmugham, Natwar Lal, Praveen Kumar K & Swapnil Rathore
Also review the answer provided by Mr Venugopal R, Benchmark Six Sigma's in-house expert.