- Assess capability for a quantitative/qualitative parameter
1. Verify the specification
The spec is ..., The tolerance is ..., Is it okay to ask the customer?
2. Collect a data sample
long-term or short-term?
Count the occurrence of defects
Caluculate the proportion of defects
3. Calculate Cp, Cpk
qualitative parameter) change from Z to Cp, Cpk, etc
- Estimating Cp, Cpk
- The short-term or long-term? -> Z-Shift
If the initial data was given as 3s in the short- term, the conversion to long- term would be as follows: 3s-1.5s=1.5s
Other conversion:Cpk=ZST/3, Ppk=ZLT/3, ZST=1.5+ZLT
● Process capability index (Wikipedia)
● 6.1.6 What is Process Capability?
NIST/SEMATECH e-Handbook of Statistical Methods, http://www.itl.nist.gov/div898/handbook/
● Z Shift
● 工程能力分析－Capability Analysis (Japanense)