Sample Size Calculation for PPM (Parts Per Million) Prediction

T

tohbin

#1
I'm asked to calculate the appropriate sample size to inspect for a process with a process average in the range of 200-500 ppm. Is there any particular formula to calculate the sample size so that a defect can be catched?
Anyone pls advise.
Thanks.
 
Elsmar Forum Sponsor
D

Dave Strouse

#2
Would like to help

Tohbin -
I'm sure others like myself would like to help, but you provide insufficient information.

Is it attribute or variable data?

What do you mean by inspect? Inprocess indicator? Accceptance sample? What is your technique?

What risk are you amiable to? Both Alpha and Beta.

Do you have any knowledge of the extant variability in the process?

There are probably other factors, but we can't even begin until you give more information.
 

Mike S.

Happy to be Alive
Trusted Information Resource
#3
Tohbin,

As Dave mentioned this is a very complex statistical question, even though it doesn't seem so at first. I'm no statistics guru, (I'm knowledgable enough to be dangerous), but I think it would help if you got a copy of, or did a Google search for information on, MIL-STD-105E and/or ANSI Z1.4-1993. These standards involve acceptance sampling and I am sure there are internet sites that can give you a decent amount of background knowledge on them and the basic statistical principals involved so that you can answer your question.

Hope this helps -- let us know. :bigwave:
 
N

Nadeem A.

#4
Re: Sample size calculation

Originally posted by tohbin
I'm asked to calculate the appropriate sample size to inspect for a process with a process average in the range of 200-500 ppm. Is there any particular formula to calculate the sample size so that a defect can be catched?
Anyone pls advise.
Thanks.
Tohbin,

A Handbook is attached in the thread "Number of responses".

http://elsmar.com/Forums/showthread.php?s=&threadid=6022

Chapter 4 of the handbook might resolve your issue.
 
T

tohbin

#6
PPM

I'm using attribute data. Inspection here is carried out on a testing process where the product is inspected for any kind of defects induced after the testing process. I only have data that shows the process average is around 200 - 500 ppm. I just want to know what should be the number of samples to be inspected in order to make sure that my testing process is performing well.

Hope this info is sufficient to answer my question.

THanks.
 
R

Rick Goodson

#7
tohbin,

Thanks for reposting with more information. Unfortunately I am still confuse because of the terms you are using, test and inspection. Is this an inspection after a test to determine if the test is operating correctly or is this simply the number of units to test to assure the process average is 200 - 500 ppm?

If you want to determine how many units to sample inspect to assure the ppm is 200 to 500, you need to know what risk level you are willing to accept that you might make a bad decision based on the sample results. In other words, if you have a million parts and there are 200 defectives in that universe (200 ppm) how many do you have to look at to be sure there are no more than 200 ppm. You would have to look at many more to be a 99% sure than you would have to look at to be 50% sure. Another complication is the sample size to discriminate between 200 ppm and 100,000 ppm will be much smaller than the sample size to discriminate between 200 ppm and 1,000 ppm.

As Mike and Dave indicated, this is not a simple question, it involves determining both supplier and customer risk factors. My suggestion is you need to learn more about the basics of sampling. There are a number of good texts available. Ed Schilling has an excellent advanced text that is available through ASQ. Dale besterfield's book, Quality Control, has good sound basic information on setting up a sampling scheme.
 
Thread starter Similar threads Forum Replies Date
H Sample Size Calculation (Confidence Interval and Reliability) - Medical Devices Reliability Analysis - Predictions, Testing and Standards 6
V Sample Size Calculation for Image Analysis - Microscopy Inspection, Prints (Drawings), Testing, Sampling and Related Topics 2
J Minitab Sample Size Calculation: 1 Sample t vs Minimum Sample Size for Means Using Minitab Software 3
P Sample Size Calculation help needed Reliability Analysis - Predictions, Testing and Standards 4
C Sample Size Calculation Formula for Process Capability Statistical Analysis Tools, Techniques and SPC 25
P Sample Size for Capability Calculation Inspection, Prints (Drawings), Testing, Sampling and Related Topics 33
D Validate 99.5% reliability 90% confidence - Sample size calculation Reliability Analysis - Predictions, Testing and Standards 4
U The Importance of Correct Sample Size Calculation - Greek Alphabet Soup Book, Video, Blog and Web Site Reviews and Recommendations 7
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) 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 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
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
P Cleaning and Disinfection Validation Sample Size of 3? Other Medical Device Related Standards 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
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

Similar threads

Top Bottom