June 2001

Vol. 3, No. 6


Quality Quiz
from Dr. Cleary

Congratulations! 
You're right!

You are correct. A capability study involves three sources of information: specifications, estimated sigma, and process average. Cpk uses these summary statistics. It does not compare individual data points to the specifications.

For a complete explanation of this solution or to learn more about Cpk, go to http://www.pqsystems.com to read a paper by SPC project manager Matthew Savage, "How can Cpk be good with data outside the specifications?" 

Copyright 2001 PQ Systems.

Please direct questions or problems regarding this web site to the Webmaster.