Testing for Process Confidence - Sample Size

M

Mark Smith

#1
#1
Here's the problem.

I want to know how many pieces from some process I need to test (and what the acceptable failure number would be) if I need the process to produce pieces with 95/95 confidence and reliability and I know nothing else about the process. If any failure occurs, how many additional pieces must be tested to achieve the same level of confidence and reliability? I believe I would begin by testing 60 pieces and allow zero failures to achieve this goal. Am I right? explain!
 
Download Free White Paper
Elsmar Forum Sponsor
D

Don Winton

#2
#2
I apologize for the delayed response. I have 'computerless' at work and the one at home is sorta acting up. Work is OK now and I will have an answer to your request in a day or so. Again, my apologies.

Regards,
Don

------------------
Just the ramblings of an Old Wizard Warrior.
 
D

Don Winton

#3
#3
There is an extensive discussion on sampling, confidence, sample sizes, etc at:

Sampling Plans

Read thru this and if you any more questions, please ask.

Regards,
Don
 
D

Don Winton

#4
#4
Mark Smith Wrote:

Don,

"Thom R Nichols" wrote an article in the June 1997 issue of MDDI Magazine ( Assessing Pass/Fail Testing When There Are No Failures to Assess )that provides a plan for assessing pass/fail testing when no failures occur. Using his chart, I selected 60 samples with zero rejects for 95% confidence. The question is "If a failure occurs, how many additional units need to be tested over 60 with zero additional failures for me to have the same level of confidence in the process producing the product in question?" Can you explain it to me? My statistical background is very limited.

Now I understand the question, I think.

You selected 60 samples with 95% confidence, therefore, from Table I, you were expecting a long term failure rate not to exceed 6.0%. But you had one failure. Now, how many additional units do you have to test to achieve the same 6.0% long term failure rate? Is that it? Let us assume it is.

From Table I, if you test 100 units with one failure, the long term failure rate is predicted to be 5.4%, which is 0.6% less than your original expectation of 6.0%. Therefore, I would test an additional 40 units, and with zero failures, your long term failure rate is predicted to be 5.4%. If the additional 40 units also had one failure, then you would need to work on the process and try the procedure over, based on the info presented in the article. Of course, you could always predict long term failure based on the actual failures. But, that is another story. Test the next 40 and if there are additional failures, we can discuss it then.

Can you explain it to me?
Click to expand...
Not really. While I understand why they are presenting this information, I do not know how they derived the charts. The authors chose not to present the statistical theory and I do not have access to references 1 or 2. If you know where they can be found on the web, let me know. My local library sorta sucks in this department. Sorry.

Regards,
Don
 
You must log in or register to reply here.
Thread starter Similar threads Forum Replies Date
J Microbiology Testing - Managing a Microbiology Process Hospitals, Clinics & other Health Care Providers 2
R Testing a Product Recall Process IEC 27001 - Information Security Management Systems (ISMS) 8
Sam Lazzara Lot Release Testing versus Process Validation Studies Qualification and Validation (including 21 CFR Part 11) 9
M Manufacturing Process Validation Destructive Testing Sampling Plan Advice Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
C Safety Tests Required for In-Process Testing of Medical Devices IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
B Pouch Sealing and Peel Testing Process Improvement ISO 13485:2016 - Medical Device Quality Management Systems 10
M Application of Special Process - Validation and FAI in Wind Tunnel Testing AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 3
A Testing Process Audit - Defining a Process Compliance Mechanism Software Quality Assurance 2
Q Process Impact Validation Testing - Polishing process Capability, Accuracy and Stability - Processes, Machines, etc. 2
J Process FMEA in a testing facility IATF 16949 - Automotive Quality Systems Standard 9
J Process Audit questions on Ultrasonic and Resonance testing Process Audits and Layered Process Audits 4
C Is Parts/Process Average Testing SPC by Another Name? Statistical Analysis Tools, Techniques and SPC 3
C Laboratory Testing as a "Special Process" - element 7.5.2 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
M Polyurethane Foam Testing and Controlling the Foaming Process Manufacturing and Related Processes 6
A How do you structure your IC Assembly and Testing PFMEA (Process FMEA)? FMEA and Control Plans 10
D Testing process is non value added process under TS16949? IATF 16949 - Automotive Quality Systems Standard 1
P Biocompatibility testing ISO-10993 for FDA submission Other Medical Device Related Standards 7
R Tips on transitioning out of testing lab Career and Occupation Discussions 0
T Aircraft GAPP Software Testing Compliance Question AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
E Usability for Near Patient Testing Test Kit Human Factors and Ergonomics in Engineering 2
J Single Fault Testing for Secondary Circuits (60601-1 section 13.1) IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
P Medical device testing lab/service standard Other Medical Device Related Standards 1
T Cytoxtoxicity Testing Dilution Other Medical Device Related Standards 1
M Altitude testing IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
H IEC 62368-1 Scope of Testing CE Marking (Conformité Européene) / CB Scheme 3
H EMC & Safety Testing of the product with the same Sr. No. for EC Declaration CE Marking (Conformité Européene) / CB Scheme 3
A Non-medical device testing in the medical system IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
H Is testing according to IEC 60601-1 & IEC 60601-1-2 mandatory for a device being registered under MDR? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
W CQI-9 Testing Fluids Manufacturing and Related Processes 0
XRAY_3121 Class II heating pad - does the power supply have to have IEC 60601-1 testing?? US Medical Device Regulations 5
T Testing for proving food safety on USP class vi material RoHS, REACH, ELV, IMDS and Restricted Substances 0
J Risk Analysis for Proficiency Testing Reliability Analysis - Predictions, Testing and Standards 1
Rene Minassian Control of (TMME) Testing and Measurement Equipment Oil and Gas Industry Standards and Regulations 2
M Is complete testing required as per ISO 10993 for materials used in orthopedic implants or is literature review route possible Other Medical Device Related Standards 3
B A testing lab within an organization ISO 17025 related Discussions 10
B Package integrity Testing failure ISO 13485:2016 - Medical Device Quality Management Systems 7
R Basic Lab Practices - related to ISO 17025 testing labs ISO 17025 related Discussions 1
N Microbial testing on food packaging materials Food Safety - ISO 22000, HACCP (21 CFR 120) 3
A Stability Testing of a device with sterile fluid pathway claim Other Medical Device and Orthopedic Related Topics 1
M Cosmetic Shelf Life Testing Misc. Quality Assurance and Business Systems Related Topics 10
S Safety testing IEC 60601 series Medical Device and FDA Regulations and Standards News 2
M EE's - Laptops/Printer Change and Emissions Testing IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
keya1tos EU to UK plug adapter correct testing standard CE Marking (Conformité Européene) / CB Scheme 9
D IEC 60601-1-2: Is EMC immunity testing required for a device without essential performance? IEC 60601 - Medical Electrical Equipment Safety Standards Series 25
M Oral irritation testing Medical Information Technology, Medical Software and Health Informatics 0
A Fire Testing - EN 50339 Not 20 minutes ISO 17025 related Discussions 0
M Biological testing at the end of the real time of MD Other Medical Device Related Standards 3
M In Vitro irritation testing according to ISO 10993-23 ISO 13485:2016 - Medical Device Quality Management Systems 2
R SaMD Performance Testing US Medical Device Regulations 5
J 'Failure rate leading to false-negatives and repeat testing' - MDCG and Common Tech Specs Other Medical Device Regulations World-Wide 0

Similar threads

Top Bottom