Step 3A: Choosing the Correct Control Chart (Discrete Data)
If the data type that needs to be charted is discrete, then it must fall between one of binary or count types. As the name suggests in case of binary distribution, there are only two possibilities, success and failure, defective and not defective, whereas in the case of count type distribution there may be more…
Closing a Six Sigma Project
As we have seen, Six Sigma is an elaborate methodology. It requires time to learn and even more time to successfully implement. However, as we have also seen that there is a golden pot at the end of the rainbow. Countless organizations have transformed their operations based on their Six Sigma capabilities. Nowadays, having processes…
Conducting the Knowledge Transfer
The Six Sigma project is not complete until the concerned personnel who have to operate the process have the know-how to do so. Many Six Sigma projects have failed because the project team was overjoyed at achieving success. However, one must not forget that improvements are only on paper until they are implemented. And there…
Just like there are many types of discrete data charts available, there are also many types of continuous control charts available. The Six Sigma process methodology prescribes which chart must be used when. The prescription in the case of continuous data points is largely based on sample size.
Below is the list of the different control charts that need to be used for different sample sizes:
Individual Chart: In the case of an individual data chart, each observation is plotted as a separate data point. This means that there is no rational subgrouping of data. This chart must therefore be used when the sample size equals 1.
Moving Range Charts: Unlike the individual data chart, the moving range chart plots the difference between two data consecutive points. The sample size of this type of control chart is therefore 2. Here the rational subgrouping of data points is based on whether they are consecutive. The moving range data charts therefore have one less data point as compared to the individual charts.
X Bar R Chart: The X bar and R chart are used to control a process when the sample size is small and constant. This is because in small sample sizes, the range of the sample approximates the standard deviation, which would be pointless to calculate, given the small size.
The X bar and R Chart are actually two different charts, which need to be looked in tandem to understand the behaviour of a process. The X bar chart shows the average performance of the process. The R chart which plots the difference between the smallest and largest value explains the variability of the process.
X Bar S Chart: The X bar and S charts are used when the sample size used to conduct the study is large and/or variable. As in the case of X bar and R chart, X bar and S charts too have a number of values. The X bar chart ensures that the mean of the process is in control whereas the S chart monitors the standard deviation. When used in tandem, they help monitor the performance of a very large process with relative ease.
Article Written by
Himanshu Juneja, the founder of Management Study Guide (MSG), is a commerce graduate from Delhi University and an MBA holder from the esteemed Institute of Management Technology (IMT). He has always been someone deeply rooted in academic excellence and driven by a relentless desire to create value. Recently, he was honored with the “Most Aspiring Entrepreneur and Management Coach of 2025 (Blindwink Awards 2025)” award, a testament to his hard work, vision, and the value MSG continues to deliver to the global community.
Article Written by
Himanshu Juneja, the founder of Management Study Guide (MSG), is a commerce graduate from Delhi University and an MBA holder from the esteemed Institute of Management Technology (IMT). He has always been someone deeply rooted in academic excellence and driven by a relentless desire to create value. Recently, he was honored with the “Most Aspiring Entrepreneur and Management Coach of 2025 (Blindwink Awards 2025)” award, a testament to his hard work, vision, and the value MSG continues to deliver to the global community.
Your email address will not be published. Required fields are marked *
