Pdf process capability and capability index cp and cpk. It will also attempt to explain the differences between process capability and process performance. The difference between cp and cpk shows that as well as being able to indicate the capability of the process to produce within specification, in cpk, there is an indication of the ability of the process to conform to the target value. Unlike the cp, the cpk is measured using standard deviation, specification limits and mean. The main difference between pp and cp on one side and ppk and cpk on the other side is whether we use complete set of data for calculation pp and ppk where we calculate real performance of the system, or we use sample preproduction, batch, logical subgroups where we calculate capability of the process. Process capability cp, cpk and process performance pp. The difference between cp and cpk and when they are used. Process capability and capability index cp and cpk. Process capability example,how to calculate cp and cpk. The difference between cp and pp, as well as between cpk and ppk, results from the method of calculating standard deviation. Learn the definitions, interpretations and calculations for cp, cpk, pp and ppk. This will help set realistic goals and aid in avoiding unnecessary pressure to the bodies involved in the process. It is worth working with more conservative pp and ppk data in case it is unclear if the sample. But the statistical measurements of cp, cpk, pp, and ppk may provide more insight into the process.
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