Sample Size, Significant Figures, Scale

G

Ge-hS

#1
One of our locations was recently cited during a Third Party audit for not establishing an appropriate sample size for calibration.

It may be that I've lost something in translation (I'm American, and my linguistic skills are very limited) - this is a finding from our Chinese facility.

They are asking:
What is the appropriate sample size for calibrating a measuring device with 0.0000 or 0.00000 decimal places of precision?

Frankly, I thought Calibration was a check, and that all the sampling sizes and everything came into play when establishing device uncertainty.

Next, I am utterly ignorant about the 0.0000 vs 0.00000 thing. I mean, I'm not approaching quantum behaviors. This is simply good old-fashioned, completely stable Microns.

Does anyone have any insight that may help?
I've been through ISO10012 and ISO5725. I may have missed it, but I didn't see Decimal Places called out for Calibration Sample Sizes?

Any help is appreciated.

(by the way, the Cove is excellent, I am glad it was able to return. And, i apologize for being a shy poster. This place has helped me a lot over the years)
 
Elsmar Forum Sponsor

dwperron

Trusted Information Resource
#2
Let me wade into these murky waters.

First, what were you being audited to? ISO 17025? FDA? A customer's requirements? If it was to a standard could you find out chapter and verse of what was being cited so we can check to see what they mean.

As for sample size based on resolution, typically you are calibrating to manufacturer specifications (unless otherwise directed). If the manufacturer calls out for a certain number of readings, or measuring at a given average setting, etc. then that is what you need to do. If there is no such guidance the instrument should be expected to report the correct value, within tolerance and uncertainty, for each reading.
 
G

Ge-hS

#3
dw -

Aw, dangit! You are making me go find some facts. I was hoping for the easy solution. I'm afraid if I lift this stone, the snake will bite me.

It was for FDA preparedness, not ISO17025, and not specific to a Customer's requirement. I would have been able to tell them ask the customer for guidance, had it been as easy as that.

I'll go ask for more facts. (And pull on my hip waders and my anti-snake bite boots - I'm afraid it is about to get deep and dangerous.)
 

dwperron

Trusted Information Resource
#4
The "sample size" flashed me back to FDA "requirements". Here is a link to a real good article explaining what they are probably looking for:

http://www.ivtnetwork.com/article/cgmp-equipment-instruments-and-calibration

A couple of the relevant points for your case are:
"Calibration should include at least three points across the full range of the instrument to help ensure linearity. Calibration experts often recommend five points: the more points, the more assurance of accuracy."
"Prepared procedures must determine when to challenge repeatability (precision) for each test point where repeatability errors can produce substantial errors (e.g., mechanical pressure indicators)."

I've run into customers who have required multiple measurements on instruments that do not have repeatability tolerances (like DMMs) that are not lumped into the overall instrument specification. In our case we just would repeat 3 measurements and verified they were all in tolerance, that seemed to make them happy!
 
Thread starter Similar threads Forum Replies Date
P Unrealistic Packaging Validation Sample Size 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 13
J Control chart for huge sample size Statistical Analysis Tools, Techniques and SPC 9
S Is there a standard for sample size during R&D phase Other ISO and International Standards and European Regulations 18
J Sample size definition in an Automotive SMT pilot lot run Misc. Quality Assurance and Business Systems Related Topics 1
E Correct way to certify hydrostatic testing when it is not 100% (and Sample Size) Various Other Specifications, Standards, and related Requirements 6
B Determining sample size for device sterility Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
D Determining of sample size for 'Operational Qualification' AQL - Acceptable Quality Level 3
F Bayes Success run Theorem for sample size during OQ&PQ Qualification and Validation (including 21 CFR Part 11) 4
I Device modifications - Clinical sample size rationale EU Medical Device Regulations 5
J Sample size for creating a data base as a reference to a tested variable Other Medical Device and Orthopedic Related Topics 6
T Sample Size for Design Validation Design and Development of Products and Processes 4
C AS9138 Sample Size Determination AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
V Acceptable maximum RSD (relative standard deviation) for an sample size Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
E Sample size for design verification of variable in single use device Design and Development of Products and Processes 19
R Sample size for clinical validation/investigation EU Medical Device Regulations 4
R Process Validation sample size selection Statistical Analysis Tools, Techniques and SPC 0
J Interesting Discussion Sample Size Determination for Medical Device Other Medical Device and Orthopedic Related Topics 9
P Is it possible to make an educated decision using a very very small sample size? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
F Sample Size for Biocompatibility Tests Other Medical Device Related Standards 4
V Firmware Verification Testing & Sample Size Software Quality Assurance 1
R Determining Sample Size for Medical Device Component Validation Inspection, Prints (Drawings), Testing, Sampling and Related Topics 0
S Surveillance Sampling Test - Determining Sample Size Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
H Sample Size Calculation (Confidence Interval and Reliability) - Medical Devices Reliability Analysis - Predictions, Testing and Standards 6
P Cleaning and Disinfection Validation Sample Size of 3? Other Medical Device Related Standards 2
V Sample Size Calculation for Image Analysis - Microscopy Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
L Heated Sealed Packages - Sample Size for OQ (Operational Qualification) and PQ Inspection, Prints (Drawings), Testing, Sampling and Related Topics 11
P Frequency and Sample Size Requirements for an MSA Studies Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
V When and How to apply the Bayes Success Run approach for Sample Size Determination Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
N Sample Size Justification for Medical Device Shelf-Life Inspection, Prints (Drawings), Testing, Sampling and Related Topics 13
C Process Qualification Sample size Document Control Systems, Procedures, Forms and Templates 6
G Sample size for IEC 60601-1-11 environmental tests IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
G IEC 60601-1-2 Sample Size issue Other Medical Device Related Standards 1
A How to calculate Mean and standard deviation without sample size in Minitab Using Minitab Software 5
D What is the minimum Sample Size for Weibull Analysis Reliability Analysis - Predictions, Testing and Standards 12
C Sample Size for Stability Testing Other Medical Device and Orthopedic Related Topics 2
M Calculating Cpk when sample size equals to 1 Capability, Accuracy and Stability - Processes, Machines, etc. 12
F Power and sample size for factorial design Using Minitab Software 4
S Sample Subgroup Size for NP/P chart - nPbar>=5 Statistical Analysis Tools, Techniques and SPC 4
U Sample size to prove parts are good with 99.73% confidence Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
F Sample Size to get Statistically Valid Data Measurement Uncertainty (MU) 6
S Low Sample Size for Gage R&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 1
S SPC Card for One Sample Size - Customer requires for all critical dimensions Statistical Analysis Tools, Techniques and SPC 8
S Determining sample size for inspection to achieve x% confidence re defects Misc. Quality Assurance and Business Systems Related Topics 10
S Determining Sample Size - AQL & LQ AQL - Acceptable Quality Level 10
B Bayes Success-Run on Attribute Data - Determining Sample Size Statistical Analysis Tools, Techniques and SPC 2
J Flammability: Testing Burn Rate with Improper Sample Size fmvss 302 Various Other Specifications, Standards, and related Requirements 1
H Factory Dictated Sample Size Justification Statistical Analysis Tools, Techniques and SPC 9
M Design Verification: "Difference" in Sample Size Calculations? Design and Development of Products and Processes 1
M Calculating Adequate Receiving Inspection Sample Size Statistical Analysis Tools, Techniques and SPC 2
S Salmonella Test Sample Size Food Safety - ISO 22000, HACCP (21 CFR 120) 3

Similar threads

Top Bottom