Can CP CPK Be Negative?

What is a good Cp and Cpk value?

We generally want a Cpk of at least 1.33 [4 sigma] or higher to satisfy most customers.

Cpk can have an upper and lower value reported.

If the upper value is 2 and the lower is 1, we say it has been shifted to the left..

What does it mean if capability index CP is less than 1?

A Process Capability Index. The ratio of the tolerance (specification, or permitted amount of variation) to the process variation. A value of 1 indicates the process variation exactly equals the tolerance. Values of less than 1 indicate the allowable variation (the tolerance) is less than the process variation.

How many Sigma is 1.67 Cpk?

6 sigmaCp = Cpk = 1.67. The sigma level is now 5 – the specifications are five standard deviations away from the average. The out of specification has decreased to 0.57 ppm. The fourth curve represents that magical 6 sigma level.

What is CP CPK?

Cp and Cpk, commonly referred to as process capability indices, are used to define the ability of a process to produce a product that meets requirements. … Specifications are normally defined in terms of nominal (+/-) tolerances or ranges (low to high.

Can CP be less than CPK?

Cpk represents the difference between the actual process average and the closest specification limit over the standard deviation, times three. By convention, when the Cpk is less than one, the process is referred to as incapable. … The Cpk index can never be greater than the Cp, only equal to it.

What does a Cpk of 1.33 mean?

Cpk = or >1.33 indicates that the process is capable and meets specification limits. Any value less than this may mean variation is too wide compared to the specification or the process average is away from the target.