Processes Effectiveness (Cp, Cpk) and Processes Performance (Pp, Ppk) – What is the Variation?

Regarding Half dozen Sigma top quality strategy, procedure show was said to the company given that a beneficial sigma top. The better the fresh new sigma height, the greater the process is carrying out.

Another way to report process capability and process performance is through the statistical measurements of C_p, C_pk, P_p, and P_pk. This article will present definitions, interpretations and calculations for C_pk and P_pk though the use of forum quotations. Thanks to everyone below that helped contributed to this excellent reference.

Definitions C_p= Process Capability. A simple and straightforward indicator of process capability. C_pk= Process Capability Index. Adjustment of C_p for the effect of non-centered distribution. P_p= Process Performance. A simple and straightforward indicator of process performance. P_pk= Process Performance Index. Adjustment of P_p for the effect of non-centered distribution.

Interpreting C_p, C_pk “C_pk is an index (a simple number) which measures how close a process is running to its specification limits, relative to the natural variability of the process. The larger the index, the less likely it is that any item will be outside the specs.” Neil Polhemus

“If you hunt our shoot targets with bow, darts, or gun try this analogy. If your shots are falling in the same spot forming a good group this is a high C_p, and when the sighting is adjusted so this tight group of shots is landing on the bullseye, you now have a high C_pk.” Tommy

Whether your vehicles is a lot smaller than the latest driveway (Half a dozen Sigma techniques), it does not amount for folks who playground they just around; it will match and you have more than enough room on sometimes top

“C_pk measures how close you are to your target and how consistent you are to around your average performance. A person may be performing with minimum variation, but he can be away from his target towards one of the specification limit, which indicates lower C_pk, whereas C_p will be high. On the other hand, a person may be on average exactly at the target, but the variation in performance is high (but still lower than the tolerance band (i.e., specification interval). _pk will be lower, but C_p will be high. C_pk will be higher only when you r meeting the target consistently with minimum variation.” Ajit

In such case together with C

“Consider a car and a garage. The garage defines the specification limits; the car defines the output of the process. If the car is only a little bit smaller than the garage, you had better park it right in the middle of the garage (center of the specification) if you want to get all of the car in the garage. If the car is wider than the garage, it does not matter if you have it centered; it will not fit. If you have a process that is in control and with little variation, you should be able to park the car easily within the garage and thus meet customer requirements. C_pk tells you https://datingranking.net/tr/chinalovecupid-inceleme/ the relationship between the size of the car, the size of the garage and how far away from the middle of the garage you parked the car.” Ben

“The value itself can be thought of as the amount the process (car) can widen before hitting the nearest spec limit (garage door edge).C_pk =1/2 means youve crunched nearest the door edge (ouch!)C_pk =1 means youre just touching the nearest edgeC_pk =2 means your width can grow 2 times before touchingC_pk =3 means your width can grow 3 times before touching” Larry Seibel

Interpreting Pp, Ppk “Techniques Abilities List fundamentally attempts to ensure if for example the shot you to you have got made throughout the process is capable to meet Buyers CTQs (requirements). It is different from Process Capabilities in that Techniques Efficiency only can be applied to a certain group away from thing. Samples on the batch may prefer to getting a bit large so you can become member of your variation in the group. Processes Performance is only made use of whenever process-control can’t be examined. A typical example of it is to possess a short pre-design focus on. Process Performance essentially spends decide to try sigma in formula; Techniques capabilities spends the procedure sigma worth calculated away from sometimes the brand new Moving Variety, Range otherwise Sigma manage maps.” Praneet