In the last post we looked at the different process capability indices like Cp, Cpk, Cpm etc. But there is also Pp and Ppk indices that measure process performance. There is a fundamental difference between the two types of indices.
We will now try to understand the difference between process capability and process performance.
And when to use what capability index?
Process capability measures the ability of the process to consistently produce output within specification limits. Process capability indices are calculated assuming the process is statistically stable i.e. has only common cause variation.
Process Performance is an estimate of the process capability during initial setup. The indices are calculated assuming the process is unstable. Such a process has both common and special cause variation. A comparison between process capability and process performance helps understand the difference between the two.
Have you used Cp, Cpk or Pp, Ppk for measuring your process capability? We would love to hear from you at info@sybeq.com.
We will now try to understand the difference between process capability and process performance.
And when to use what capability index?
Process capability measures the ability of the process to consistently produce output within specification limits. Process capability indices are calculated assuming the process is statistically stable i.e. has only common cause variation.
Process Performance is an estimate of the process capability during initial setup. The indices are calculated assuming the process is unstable. Such a process has both common and special cause variation. A comparison between process capability and process performance helps understand the difference between the two.
Have you used Cp, Cpk or Pp, Ppk for measuring your process capability? We would love to hear from you at info@sybeq.com.
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