Cpk is calculated using the formula…
So we think about this formula, Cpk is the minimum distance of the process average from either specification limits.
Scenario 1
Consider a process as shown in figure 1. The process average is closest to the Lower Specification limit.
In this case, since process average is less than LSL, Cpk is negative.
The area of the histogram or distribution curve in red indicates parts that are below the Lower spec limit. All these parts are rejected.
Scenario 2
Consider another process as shown in figure 2. The process average is closest to the Upper Specification limit. In this case as process average is greater than USL, Cpk in this case is also negative.
The entire area under the distribution curve is red i.e. all parts are rejects as they are above the Upper spec limit.
What does a negative Cpk indicate?
As seen from the examples above, a negative Cpk indicates that the process average is outside the specification limits. Most of the readings are outside the specifications i.e. they are rejects.
Have you come across a negative Cpk? What did you think about it?
3 comments:
No, You can not have a negative Cpk, if the value you obtain is negative then your process is not capable therefore, there are not such thing as Cpk. So, yes you can have negative Number but not Negative Cpk.
What is the meaning of negative value of CP
I’m impressed, I need to say. Actually hardly ever do I encounter a weblog that’s both educative and entertaining, and let me inform you, you have got hit the nail on the head. Your concept is excellent; the problem is something that not sufficient persons are speaking intelligently about. I am very blissful that I stumbled throughout this in my seek for something relating to this. online casino bonus
Post a Comment