Sample Size Determination - Medical Devices

K

Kary13

#1
Ok... another newbee question :eek:

I recently started working for a new company which product is a medical device, for the time-being, limited to software. We are preparing for ISO 13485 audit.

My question:
The manufacturing process for the software has not been decided completely yet (outsourced or not). Manufacturing process, for us, "simply" imply burning cd, label & pack... I am doing a procedure for purchased products verification but I am having trouble defining stats variables. I do understand (or think I am) the AQL but I cannot understand how you can determine the sample size regardless of the population size (or size of the lot). Doesn't the sample size should vary with the size of the lot and the quality assured by the manufacturer?

Thanks for your help...
 
Elsmar Forum Sponsor
T

timference

#2
Re: Sample Size Determination

Karey13,

requirement for ISO/TS 16949 may vary from the standard you are auditing to but here is my thoughts. First, AQL sampling is a good start. However you need to take into consideration other factors when creating a sampling plan. Some considerations are:

Past performance from the supplier

The importance of the part being inspected (a blank jewel case may need little inspection but the printed jacket may require mor inspection)

What types of inspections are being done a the supplier. (sometimes the review of there data may suffice. We have many suppliers taht are dock to stock and onoly send the process results(SPC data)).

I would suggest you base your initial sampling plan on the importance of the component coming in and of the past performacne of the supplier. This should also be acceptable to the requiremetn in the standard you are using.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#3
Re: Sample Size Determination

unless you have very small lots and categorical data (pass fail, counting data, also known as 'attributes' data) the sample size is nto dependent on the lot size. The sample size is dependent on the amount of actual variation the lot has - or that you are looking to detect - and the amount of 'confidence' you want in your inspection.


Are you working with categorical or continuous (measurable or 'variables') data?

I can attach a spreadsheet and a brief description of the formulas for categorical data if you'd like....
 
K

Kary13

#4
Re: Sample Size Determination

Hum... stats theory is a bit far-away I realise...

We'll produce medical devices (for now, only software) in relatively small quantity since the targeted user is not general public but particular classes of diagnosticians. It might be it: I don't see how I can have a sample size of 60 (for example, CDs or labels) if I produce 15 units per year...

For the current product, purchased products would either pass or fail (nothing to measure). Lot size will be max 100 (guessing) and we would not have that many lot per year (1 or 2?) hence wondering if it is even possible to have a complete sampling plan including different levels of inspection procedure like normal, tightened....

If you can provide me with guidelines, Bev D, I would really appreciate it!
 
K

Kary13

#5
Re: Sample Size Determination

To simplify things for everybody, is this approach suitable:

Using standard MIL-STD-105E (and eventually ASQ z1.4 when I receive it):

- Use an AQL of 1.0 which seems ok in the medical field
- Use single sampling (is this the easiest approach in terms of implementation and paper work? we do not have that many resources for now...)
- Determine the sample size from table I - Sample size code letters
- Perform tests
- Use table II-A - Single sampling plans for normal inspection to determine if lot is accepted or not
(if number of defect units <= acceptance nb = lot accepted;
if number of defect units > acceptance nb = lot rejected)

Since we are a small company, that we won't have regular shipping of the same products shipped (for now), I would be tempted not to implement switching of level of inspections since it seems to me that it will require more time and paperwork than the benefit we would gain from it... Can we do that? If so, would it cause a problem if a lot is rejected and manufacturer sends another one?
 
Thread starter Similar threads Forum Replies Date
C AS9138 Sample Size Determination AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 1
J Interesting Discussion Sample Size Determination for Medical Device Other Medical Device and Orthopedic Related Topics 19
V When and How to apply the Bayes Success Run approach for Sample Size Determination Inspection, Prints (Drawings), Testing, Sampling and Related Topics 4
Statistical Steven Continuous Data Analysis Sample Size Determination Six Sigma 3
A Destructive Test Sample Size Determination Statistical Analysis Tools, Techniques and SPC 4
P Repetition (sample size) for measuring equipment accuracy determination General Measurement Device and Calibration Topics 1
S Determination of sample size for product audit IATF 16949 - Automotive Quality Systems Standard 1
A Clinical assessment sample size - Medical device Class IIb implantable (93/42 directive) EU Medical Device Regulations 2
P Sample Size for Distribution Simulation Testing Inspection, Prints (Drawings), Testing, Sampling and Related Topics 11
C Stress / Challenge Conditions for Design Verification Testing to Reduce Sample Size 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 11
K How can Acceptance Number and Reject Number be larger than Sample Size on Z1.4 Table? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 8
J Validation Sample Size for Tray Seal Qualification and Validation (including 21 CFR Part 11) 1
D Design Verification Sample Size vs Repeats Statistical Analysis Tools, Techniques and SPC 9
M Minimum sample size - Guidance and statistical rationale Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
P Unrealistic Packaging Validation Sample Size 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 39
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 5
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
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 20
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
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
G Sample Size, Significant Figures, Scale General Measurement Device and Calibration Topics 3
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
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

Similar threads

Top Bottom