诺基亚请某咨询公司做的-NOKIA制程能力控制（英文版）.ppt55

Two Types of Processes
All processes have:
Natural (random) variability=> due to common causes
The Two Causes of Variation
Common Causes:
Causes that are implemented in the process due to the design of the process, and affect all outcomes of the process
Identifying these types of causes requires methods such as Design of Experiment (DOE), etc.
Special Causes:
Causes that are not present in the process all the time and do not affect all outcomes, but arise because of specific circumstances
Special causes can be identified using Statistical Process Control (SPC)
Tolerances
A tolerance is a allowed  maximum variation of a dimension.
..............................