SPC on Attributive data?
Hello everyone! 
My name is Emanuel, and I currently work as Production Engineer (the job profile is more supplier quality engineer).  I have always worked in Quality, Product Quality, Quality Engineer, Customer Quality Engineer, Supplier Quality.  


I my current assignment the RE (requirement engineer) recently defined CTQ (Critical to Quality) dimensions on drawing, but also marked as CTQ the thread of a screw for example, we are checking this by a GoNoGo gauge so we have ok/nok. Also tensile test is marked as CTQ but for this we only define min value ex. 3000N 

The management wants to us to implement SPC for all CTQ, my question is how would you handle this attributive data in this situation? Any experience with this?

Any feedback is really appreciated.
Regards,
Emanuel
 
8 Replies
Duke Okes
125 Posts
Attribute SPC charts include c, p, np and u charts.  Whether or not they will work well will depend partially on sample size, which you can control somewhat by frequency of plotting the data, although this may also impact the ability to respond in a timely manner.
Thanks Duke! I will look in to those charts and frequency of plotting the data. 
Trish Borzon
609 Posts
Hi Emanuel - Welcome to myASQ & thanks for posting a questions right away.  This is a great community & I'm glad Duke Okes‍ helped - Thanks Duke! 
Hope you enjoy the community 
Trish 
Duke Okes
125 Posts
Trish, ASQ probably has some online resources that might help.  I didn't take time to look them up.
Trish Borzon
609 Posts
Gretchen Peterson‍ - can you help? 
thanks :D 
Trish 
Thanks for the tag, Trish Borzon‍.

Emanuel Alexandru Orzan‍, a good starting point is the Statistical Process Control Learn About Quality page: https://asq.org/quality-resources/statistical-process-control

Of most use to you may the additional references listed at the bottom of the page.  I'd also encourage you to look at what is available in the Resources tab, especially the articles related to this topic. 

I hope that this is helpful to you!

Gretchen
Hello all, 

Thank you very much for your help. 

Thank you very much Gretchen Peterson, this page is really helpful! 

Regards, 
Emanuel 
Hi Emanuel - I would recommend you to consider, in addition to many other fantastic resources available through ASQ, the following handbook -  Introduction to Statistical Quality Control by Douglas Montgomery (any edition), which I was lucky to come across in the beginning of my Quality journey.

Regards,
Alexander Kholodov
ASQ CQE