Sample Size for Short Term & Long Term Process Capability

kedarg6500

Quite Involved in Discussions
#1
Dear All

It is said that sample size for short term process capability study shall be min 30 consecutive readings with subgroup size 1 & long Term process capability study it should be min 100-125 readings, with subgroup size 2-4. But I could not find any reference.

Looking for valid reference from AIAG manuals, ASQ OR SPC/SQC book.

Pl help

Kedar
 
Elsmar Forum Sponsor

Bill McNeese

Involved In Discussions
#2
The 30 is fairly common for initial capability studies (e.g. PPAP), but it does depend on the process. On the long-term studies, it is not a question of number but of time. You want enough time to pass so that all sources of variation have an opportunity to be present (e.g., different suppliers, different operators, different temperatures, etc.). That might be a month, it might be much longer. A "long term" study with 125 widgets made right in a row is not long term.
 

Darius

Quite Involved in Discussions
#3
Dear All

It is said that sample size for short term process capability study shall be min 30 consecutive readings with subgroup size 1 & long Term process capability study it should be min 100-125 readings, with subgroup size 2-4. But I could not find any reference.

Looking for valid reference from AIAG manuals, ASQ OR SPC/SQC book.

Pl help

Kedar
As I have readed, 100, sample size 5 means 25 cosecutive samples (of 5 as sample size), but what is on this number?..., well, I think:2cents:, It's just normality asumption (plus something else to be sure), rememeber that the normality test has a table until 60 samples, so with 120 samples (the double), is just to be sure that normality is accomplished.

You can :2cents: just get rid of outliers and obtain the sample (not contaminated by outliers), and so the parameters must represent the process. There are several outilers detection methods, like Chauvenet, Grubbs, interquartile distance, or something else. calculate non parametric capacity indexes or take for grantes normality (if the process has demostrated such behaviour).

note: I have done studies, were I used outlier elimination, and obtain the mean with a few data points (less that 200) that I need 10,000 or more samples to obtain (without outlier elimination).
 
Thread starter Similar threads Forum Replies Date
P Short Run Charts - Sample size N=1 Statistical Analysis Tools, Techniques and SPC 2
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 9100, Nadcap and related Aerospace 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
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
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
Similar threads


















































Top Bottom