# Cmk is defined as a Capability Index for a Stable Machine

S

#### SteveT

Could someone please describe to me what statistical index Cmk is, what it means, and how to calculate it.

Many Thanks SteveT

F

#### freeda

Cmk is defined as a capability index for a stable machine. It uses the same formula as Ppk.
Cmk is a short term study of a machine capability. Whereas Ppk is a short run study for a process.

D

#### Don Winton

I do not know about Cmk, but Cpmk is defined as:

Cpmk = (USL – LSL)/(6*(sqrt(StandardDeviation^2+(mean – T)^2)))​

Where T = Target Value.

This link http://www.asq.org/pub/jqt/past/vol32_issue4/qtec-440.pdf gives some additional info. This is a PDF file, so you will need Acrobat Reader to access it.

Hope this helps.

Regards,

Don

------------------
I was better but I got over it.

D

#### Don Winton

...what it means...

Ooops. Forgot. Cpmk is used when the tolerances are not symmetric about the target.

Regards,

Don

------------------
I was better but I got over it.

N

#### narfeldt

Ain't Cmk=revised rates of machine capability and calculates by the formula:

Cmk = 2((UTL-Mean)/(Xmax-Xmin))
Cmk = 2((LTL-Mean)/(Xmax-Xmin))
Cmk = the lowest value of above formula

Is this incorrect?

------------------
/Best wish Narfeldt

[This message has been edited by narfeldt (edited 07 June 2001).]

#### Marc

##### Hunkered Down for the Duration
Staff member
Blast from the Past!

Calibration or Verification -> Cm and Cmk, etc. Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 3
How is the Cmk and Cpk calculated? Statistical Analysis Tools, Techniques and SPC 0
Function in french called "numbre de posage(s)" - CMK Question Quality Tools, Improvement and Analysis 3
Excel Spreadsheet Template to calculate Cmk (Machine Capability) wanted Capability, Accuracy and Stability - Processes, Machines, etc. 2
Q Machine Capability Study - Cpk (Cmk) of an R/F testing machine Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
L Fastening Process Cmk study - Bolt Torque Statistical Analysis Tools, Techniques and SPC 1
L Multi-fixtures in one CNC lathe - How to do Cmk study? Statistical Analysis Tools, Techniques and SPC 6
F MCA calculation - problem with Cm Cmk and boundaries Capability, Accuracy and Stability - Processes, Machines, etc. 1
M Cmk (Machine Capability) - Case study Capability, Accuracy and Stability - Processes, Machines, etc. 5
C Gauge R&R Studies Bad, but Process has a Cmk of over 7 IATF 16949 - Automotive Quality Systems Standard 8
S A question about Cpk and Cmk - Can we use Cpk to replace Cmk? Capability, Accuracy and Stability - Processes, Machines, etc. 1
V Machine short term capability study with Cmk index in automotive industry Capability, Accuracy and Stability - Processes, Machines, etc. 3
Q Confused about the machine capability index Cmk Capability, Accuracy and Stability - Processes, Machines, etc. 1
D Tool Approval Process - Should we be using Cmk for tool validation Statistical Analysis Tools, Techniques and SPC 2
A Acceptance criteria for Cmk (machine capability index) Statistical Analysis Tools, Techniques and SPC 3
H Some questions about Cmk and Cpk Capability, Accuracy and Stability - Processes, Machines, etc. 2
I am confused, which Cmk value should I take and use? Statistical Analysis Tools, Techniques and SPC 6
M How to Conduct a Machine Capability (Cmk) Study Statistical Analysis Tools, Techniques and SPC 26
C Evaluating software that measures Ppk, Cmk, Cpk, PPI, etc. Capability, Accuracy and Stability - Processes, Machines, etc. 4
S Cmk and Cpk - When will we need to calculate Cmk? Machine Capability Capability, Accuracy and Stability - Processes, Machines, etc. 4
A Cpk, Cmk in Electronic Assembly (Process Capabiity) Capability, Accuracy and Stability - Processes, Machines, etc. 4
B Any ideas on setting up Capability Study spreadsheet in Excel? (CPK/CMK formulae) Excel .xls Spreadsheet Templates and Tools 4
K Cmk - What is the difference between an R&R study and Cmk? Statistical Analysis Tools, Techniques and SPC 4
D Can anyone enlighten me as to what exactly Cm / Cmk are? Statistical Analysis Tools, Techniques and SPC 1
M Cmk calculation - Small plastic parts using injection-moulding machine Statistical Analysis Tools, Techniques and SPC 2
Controlled information versus defined documents / records ISO 13485:2016 - Medical Device Quality Management Systems 3
Is there any pre-defined Control plan format/template acc. VDA? VDA Standards - Germany's Automotive Standards 0
Design and implementation of process audits as defined within IATF 16949 IATF 16949 - Automotive Quality Systems Standard 2
No Defined Shelf Life/Expiration Date - Disposable single-use, non-invasive, non-sterile Other Medical Device Regulations World-Wide 2
How are Medical Device Components and Subassemblies defined? ISO 13485:2016 - Medical Device Quality Management Systems 1
Definition Defined - Definition and meaning of "defined" Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 10
Defined Roles in Small Company ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 12
Short Term vs. Long Term SPC Study - Where is Cp and Cpk Defined Statistical Analysis Tools, Techniques and SPC 8
Validation of Processes - What is meant by 7.5.6 (a) - Defined Criteria for Review ISO 13485:2016 - Medical Device Quality Management Systems 7
J Measuring Leakage Currents with IEC 60601 defined Measurement Device (MD) IEC 60601 - Medical Electrical Equipment Safety Standards Series 15
Technical Files Sampling Rule defined in NBOG 2009-4 EU Medical Device Regulations 2
What results need to be defined in IATF 16949 Clause 8.3.4 IATF 16949 - Automotive Quality Systems Standard 3
J Deformation specification not defined in print Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
How others have defined "reaudits"? 21 CFR Part 820.22 Internal Auditing 1
R Property - What is defined as Property in ISO 14971 ISO 14971 - Medical Device Risk Management 4
C AS9100 Requirement Definition - Defined vs. Documented AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 14
X Are defined roles and responsibilities mandatory for ISO 9001? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 2
M Root Cause of 'Supplier Evaluation Not defined' Nonconformance and Corrective Action 15
J Is painting considered a Special Process as defined by ISO 9001 7.5.2? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
Preventive Action vs. Corrective Action as defined by 21CFR820 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 10
A How is Segregation of Duties defined in the IT World? IEC 27001 - Information Security Management Systems (ISMS) 4
Q Must Support Processes have defined KPI's (Key Performance Indicators)? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 2
K What constitutes (is defined as) as a Medical Device? Other Medical Device and Orthopedic Related Topics 3
External Audit re-defined Imported Legacy Blogs 4
Definition Diagnostic - Is "diagnostic" defined in the EU Medical Device Standards? Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 10