Control Charts in Process Control and Data Analysis
To answer the subject of process control in data analysis, control charts must be understood. A control chart is a graph that is used to routinely monitor the quality of statistical operations (Adams, 2014). Control charts have a mean value line in the middle, as well as lower and upper control limit lines. When determining whether a process is under control, fresh data is compared to the limits produced by previous information or evidence ("Guide to Control Charts," n.d.). If a due procedure is followed and still realized that the process is out of control regardless of all data points falling within the range of lower and upper control limit, then it is considered that it is caused by extraneous factors which need to be investigated.
Non-random patterns may exist in the illustration of control charts which requires the employment of statistical techniques to detect so that all points fit into a random pattern. If it can be isolated that only chance causes contribute to the non-randomness, then it is eliminated which will yield a 100% conformance to the process (Adams, 2014).
Indicators of an Out of Control Process
If four out of the five subsequent data points in a control chart lie on one side of the average line and is further than the standard deviation, then it is an indicator of an out of control process. Also, if two out of three data points fall on one side of the central line and deviates in more than twice the standard deviation, then a process will be out of control. Therefore, control charts are the essential tools that are used by the statistical analyst in monitoring processes and evaluating its conformity to the quality standards.
References
Adams, B. M. (2014). Control Charts, Selection of. Wiley StatsRef: Statistics Reference Online. doi:10.1002/9781118445112.stat04062
A Guide to Control Charts. (n.d.). Retrieved from http://www.isixsigma.com/tools-templates/control-charts/a-guide-to-control-charts/
