The difference between control chart and run chart is very narrow thus making it difficult to understand the difference. Control chart and run chart can be identified as statistical tools used in tracking the performance of the company within a particular period.Both these methods use time as the baseline and the performance measure as the measurement that is being tracked within a particular period. However, where they are used differs, depending on the purposes. In this article, we have discussed what control chart and run chart are, for what purposes they are used, and finally, the difference between these two methods.
What is a Control Chart?
A control chart is a specific type of a graph used to study the fluctuations within a process during a specific period. A control chart is drawn including an upper line for the upper control limit, a lower line for the lower control limit and a central line for the average,. These lines are determined according to the past data. These charts have been useful in making comparisons and in concluding on the consistency or the variations of the processes.
Benefits of using a Control Chart
• To monitor and control the ongoing process by recognizing the issues that arise.
• To predict the expected ranges of outcomes from the process.
• To determine the stability of a process.
• To analyze the patterns of the process variation from the special causes (non-routine events) or common causes (built into the process).
• To determine the areas where the quality needs to be improved in the project in order to increase the productivity.
What is a Run Chart?
In a run chart, certain values have been plotted and an average line has been drawn to clarify the movements of the data away from the average. This center line represents the middle point of the measurement that is being tracked (Refer below diagram).
Run charts are used to display the performance of a particular process within a specific period. Cycles, upward and downward trends are spotted in these charts. Run charts are primarily used in tracking the performance of a particular process which requires further improvements.
What is the difference between Run Chart and Control Chart?
Following graph has been used to clearly illustrate the difference between run chart and the control chart.
• The major differences between these two methods are that run charts have a center line that represents the middle point of the measurement that is being tracked, while control charts have a center line that represents the average of the measurement that is being tracked.
• Both these charts are drawn by plotting the data within a particular period. However, the control chart consists with an upper and a lower control limit lines with a center line. (As indicated in the above figure)
• Control charts are designed to;
1) Make the necessary improvements within the process and
2) Prevent the errors occurred in the process.
• Run charts do not provide any support with the statistical control limits. Therefore, when it is required to make changes in the process, it may be useful to add more variations to the process rather than reducing the variations.
Based on the goals of the project, the most suitable chart can be chosen. Usually control charts provide more specific information and insight to the process, compared to the run chart.