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What is Process Capability?Process capability compares the output of an in-control process to the specification limits by using

capability indices. The comparison is made by forming the ratio of the spread between the process

specifications (the specification "width") to the spread of the process values, as measured by 6 processstandard deviation units (the process "width").

The Process Capability is a measurable property of a process to the specification, expressed as a process

capability index (e.g., Cpk or Cpm) or as a process performance index (e.g., Ppk or Ppm). The output of

this measurement is usually illustrated by a histogram and calculations that predict how many parts will

be produced out of specification (OOS).

Process capability is also defined as the capability of a process to meet its purpose as managed by an

organization's management and process definition structures ISO 15504.

Benefits of AnalysisSix Sigma methods have become very popular among businesses and organizations everywhere. There

are many Six Sigma tools that can be used for a wide variety of reasons from measuring productivity to

keeping up with company progress. Capability analysis is one such statistical tool that can be very useful

for a number of reasons.

Capability analysis comes up twice in the course of the entire Six Sigma process. It provides a number of

different ways to measure capability. Capability analysis allows organizational leaders to measure the

variation and bias of a particular process against specifications. Here, specifications are defined as the

requirements of the customer. The number that is acquired comes in the form of a statistic that

indicates the level at which the process actually meets the customers needs. You can see the variations

in the form of diagrams that will accurately depict important data that will help you reach useful

inclusions.

Capability can be measured in a number of ways. All of the measurements you can yield are simply

different ways of expressing the same idea. There arent many differences between measuring methods

so you can easily choose the one you prefer. So why should you use capability analysis in the context of

Six Sigma? One reason is baseline process performance and another is to measure improvement. When

you are measuring baseline performance, you want to figure out how well the intended function is

performed in terms of the process at hand. This is what capability truly is, and illustrates why this tool is

useful during the Six Sigma Process. Before you can make changes, you need to know where the process

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stands right now. That is what will serve as your baseline, and it is also what will allow you to go back

later and make any necessary changes.

Once the baseline has been established, its time to figure out what improvements need to be made.

You will then formulate a plan to put them into place. After implementing this plan, you will allow the

process to continue running for quite a while so you can clearly assess its success once more. You will

compare the new performance to the baseline in an effort to determine the amount of improvement

that been made through the entire duration of using Six Sigma and capability analysis.