On-Demand Manufacturing
The Millennial generation has got used to living in an on-demand world. They buy food on demand, hire cabs on demand and even take exams on demand! It was only a matter of time before the manufacturing industry jumped to the on-demand bandwagon as well. The truth is that there is a significant upside to […]
Production and Operations Management – Meaning and Important Concepts
Introduction The very essence of any business is to cater needs of customer by providing services and goods, and in process create value for customers and solve their problems. Production and operations management talks about applying business organization and management concepts in creation of goods and services. Production Production is a scientific process which involves […]
Finished Goods Supply Chain Operations
FG Supply Chain consists of all activities involved in movement, storage and distribution of Finished Goods from the Delivery point of Plant to the Point of Sale. In the case of global supply chains, supply chain management gets more complicated with the variations arising out of different countries regulations and logistical practices. Computer Hardware supply […]
Tips for Writing Effective Problem and Goals Statement
Although the Six Sigma process has tried to make the process of developing problem and goal statements into a science, however in reality it still remains an art. This combined with the fact that goal and problem statements go a long way into the execution of the project make it important to understand what are […]
Change Management and Organizations
Every Christmas, Apple plays to the gallery where all Americans and the rest of the Apple fans across the world wait eagerly for the new promised product of the future and expectantly Apple has unveiled the new, slimmer and improved I Phone 5G. It is no secret that Apple is a cult world over. With […]
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.
Your email address will not be published. Required fields are marked *
Step 3A: Choosing the Correct Control Chart (Discrete Data)
February 12, 2025
