Process Capability (Measure)
Process Capability Index
Based on all batches and the population standard deviation
How does the Black Belt determine Mean shift?
Check the Cp value first, and then the Cpk value If Cp greater than 1 and Cpk is also greater than 1, it indicates the process is capable of performing to customer expectations.
Which one of these activities should ideally come first in the implementation of a Measure stage, normality, precision, repeatability or resolution?
Checking Resolution
What calculations are used for capability in discrete data?
DPMO or PPM
Cpk can have negative values (True or False)
False: Cpk can only have positive values
When is a process fully capable?
It has to at least reach 1.33
How to determine best fit in Non normal capability?
Look at p-value in Goodness of fit test p-value must be greater than 0.010 (p>0.010)
If Cpk=Cp
Mean is centered and process accurate, but need to assess variation
If Cpk<Cp
Mean isn't centered, variation is high
Cpk index
Process alignment-how good process delivers with respect to mean
Cp
Process capability (tolerance)how good process delivers what customer wants
Which tool is typically used for scope in Measure Stage
SIPOC
What is the most important pre-cursor for Capability studies?
Stability
Cpk negative
The process mean exceeds the specification limits
What are common goals set in process capability?
1.33 or 1.67 are commonly set as goals. 1.33 correspond to 4 sigma; 1.67 represents 5 sigma levels.
How are specification limits derived?
From Voice of customer; the customer requirements
Ppk- Process Performance Index
How well process is in delivering what customer wants, over time with respect to Mean in the long run
Pp -Process potential
How well process performs over time with respect to specifications
Process performance indices
Index based on a specific batch and sample standard deviation
CP is always greater than Cpk (True or False)
True
True/False: Cpk, Cp cannot be used for Discrete data
True
Cpk cannot be larger than Cp (true or false)
True: Cp represents the maximum capability
If Cp or Cpk <1
Variation is high, capability is low and process incapable
If Cp or Cpk>1
Variation is low, capability is high and process is Capable