Team Management during a Project
Team Member Selection Team member selection is a process that involves mapping of skills and strengths of each individual member with that of the role and the job description for which they are being hired or taken into the team. The process should take into account the perceptions of the team member regarding the role […]
International Production and Operations Management (IPOM) – Meaning, Nature and Strategies
Introduction International production and operations management deals with production of goods and services in international locations and markets. It involves management process which has to take into consideration local production market (labor and capital) and international customer requirements. Nature of IPOM The foundation for international production and operations is no different to domestic production and […]
Fiat Currency and Trade Deficit
The United States has one of the largest trade deficits in the world. Many critics have been of the opinion that it is only because of the existence of fiat currency that such huge imbalances are possible. These critics believe that if the world were to return to a gold standard, these imbalances would resolve […]
The Shock of Gray and Its Implications for the Healthcare Sector
What is meant by the Shock of Gray and its Implications? The Shock of Gray is a term used to describe the ageing of the populations in the West with the retirement of the Baby Boomer generation and the resultant “graying” of the western societies. This phenomenon has several economic implications mainly related to the […]
Privatization of Water
The world is facing a scarcity of water. Each year about 3.4 million people die due to the scarcity of water! Several million more fall sick due to the poor sanitary conditions of the water supplied. The current situation is proof of the fact that the global water supply is not being managed properly. Many […]
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 than two possibilities of the process, the number of defects still need to be counted. The difference between the two is subtle. However, given the fact that there are fixed rules governing when which chart needs to be used, the confusion is reduced.
Equal Subgroup Size: In this case, the Six Sigma process methodology suggests using the C Chart. The C Chart counts the number of defects that are happening per unit of unit. This could be per minute, per hour, per day or per week and so on. The important part here is that since the time period is fixed, so is the sample size. The C Chart will tell you how many observations from a given sample failed to meet the criteria specified by the control limits.
Unequal Subgroup Size: In this case, the Six Sigma process methodology recommends using the “U” chart. The U chart counts the rate of defects. This means that it keeps a track of the number of units that it has monitored and how many have failed the given criteria specified by the control limits. The U Chart will tell you, for example that 5/1253 units have failed to comply. Hence it does not require a fixed time period or a fixed sample size and may be more convenient to use.
Equal Subgroup Size: In this case, the Six Sigma process methodology recommends using the NP Chart. The NP chart also counts the number of defects per period of time just like the C Chart. There is however a subtle difference between the two. C Chart is used when the occurrence of defects is rare. However, NP chart uses the binomial distribution. Therefore, the occurrences do not have to be rare. As a thumb rule, if there is a chance more than 5% defects in a process, then the NP chart must be used.
Unequal Subgroup Size: In this case, the P chart is recommended. Once again, it is quite similar to the U chart. This chart calculates the defects as a percentage figure meaning that it takes into account the units that have gone through the process just like the U Chart. The U chart also uses the Binomial distribution and is used when the occurrences of defects is not rare.
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Step 3B: Choosing the Correct Control Chart (Continuous Data)
February 12, 2025
