[3.b] Process Capability Ratio (Cp) and Index (Cpk)

Operations Management Lecture Series, by Dr. Narendar Sumukadas
Click here to view the complete series:

[jamjum]

I never seen someone explain statistics in such a simple way, I have been struggling with Cp and Cpk, now it is so simple .. Thanks you very much for your efforts

[narendarsumukadas]

"Closest spec is at least 6-sigma distance from the mean" refers to a 6-sigma capable process. For a 3-sigma capable process, often considered bare minimum capability, the closest spec is only 3-sigma away.

For a 3-sigma capable process, we can fit 6-sigma (+/- 3-sigma) within the USpec-LSpec range, so Cp = 1.0. For a 6-sigma capable process, we can fit 12-sigma (+/- 6-sigma). The denominator of the Cp formula always remains "6-sigma." So, for a 6-sigma capable process Cp = 2.0.

[jamesshelton]

5 STAR!  Fantastic!, Sir you have a very clear, well-timed presentation that is easy to follow, understandable & applyable - Thank-you very much for your contribution - THOROUGHLY RECOMMENDED.

[IsabelR]

Clean and Easy to understand. Awesome.

[vemana]

Best explanation I have ever seen on process capability...

[nitindev]

Explained thoroughly in a great way, i am back to basics. Thanks a lot

[dvrhmyx]

This is fantastic. You have a fan in Singapore!

[raghavnandyal]

Excellent example and very lucid explanation! Kudos!

[nadimtabbal]

Correct me if I am wrong: the 3.4 DPMO is relative to 6 sigma where this is 3 sigma on either sides of the mean (i.e. both sides) totaling 6 sigma range, whereas 6 sigma capability producing a Cp = 2 is 6 sigma on either sides of the mean (i.e. both side) totaling 12 sigma range.

[jstopable]

Wow! This guy can really teach! Superb.

[soorajtp]

Excellent perspective-you are really a master

[mariustm]

Hello Mr. Sumukadas,

Your movies are some of the most usefully for understanding some statistical process control.
Anyway, I would need a little help on the meaning of Cp=(USL-LSL)/6Sigma.
"00:30 -> Within the tolerance range of the customer (USL-LSL) can we fit 6sigma? If yes, than the process is capable."
Another definition is that if the closest specification limit to the mean is at least 6sigma distance from the mean, than the process is capable? Than shouldn't be Cp=(USL-LSL)/12sigma?

[kavinduwijerathne]

Thanks for the excellent explaination! Easy to understand

[mohanjadhav]

Very good explanation of cp and cpk.. greatly recommended.. Sir could you please add video explaining pp and ppk?

[benteo]

Good simple explaination of Cp and Cpk. Thanks!

[nilusur]

Thank you so much...Excellent explanation... You saved me....

[Zsomb]

thank you very much for your help! Your video is very very useful! Could you pls give me an example about Cm and Cmk, the machine capabilities? Or do they function similarly to Cp and Cpk?

[athomas]

Thanks Narendar, great
I have a question regarding CpK calculation for Lab results in a pharma company? What should be the minimum number of data to get it statistically significant .  If we have only less than 3 batches / year, can we still calculate the CpK value?

[omahb]

very good explications... Thank you very much...

[tahaniqu]

I try to understand but I couldn't. Depending on what, this ruler growing taller or becoming shorter, it seems there is fundamental information missing.