As a subject matter expert in statistical quality control, I can explain the difference between CPK and PPK, which are both indices used to measure the potential or actual performance of a manufacturing process.

English Answer:

CPK stands for Process Capability Index and is a statistical measure that indicates how capable a manufacturing process is of producing output within specified limits. It is calculated by comparing the width of the process spread to the distance between the process mean and the nearest specification limit. A higher CPK value generally indicates a more capable process, with a value greater than 1.0 typically considered good.

PPK, on the other hand, stands for Performance Potential Index. It is similar to CPK but is based on actual process performance data rather than the capability of the process under ideal conditions. PPK takes into account the actual variation in the process and is a more realistic measure of the process's performance. It is calculated using the same formula as CPK, but with the actual standard deviation of the process data instead of the theoretical standard deviation.

The key difference between CPK and PPK is that CPK is a predictive measure based on the process's potential, assuming the process is in control and stable, while PPK is a retrospective measure that reflects the actual performance of the process.

中文回答：

CPK代表过程能力指数，是一种统计度量，表明制造过程产生符合规定限制的输出的能力。它通过比较过程分布宽度与过程平均值和最近规格限之间的距离来计算。一般来说，较高的CPK值表明过程能力更强，大于1.0的值通常被认为是好的。

PPK，即性能潜力指数，与CPK类似，但是基于实际过程性能数据而不是理想条件下过程的潜在能力。PPK考虑了过程中的实际变化，是对过程性能的更现实的度量。它使用与CPK相同的公式计算，但使用的是过程数据的实际标准偏差，而不是理论上的标准偏差。

CPK和PPK之间的关键区别在于，CPK是基于过程潜力的预测性度量，假设过程处于控制之下且稳定，而PPK是反映过程实际性能的回顾性度量。

read more >>

Peter. Sorry to tell, but definition of Cpk and Ppk is wrong, it��s just the other way round: Ppk is a short term analysis (mostly done with 50 or 100 samples measured) Ppk is Process Potential Capability. Cpk is long term analysis and is Continous Process capability.read more >>