# Predicting External PPM Capability from Internal PPM

Z

#### z28tt

Hello stats gurus:
I work at an aerospace job shop that machines about a million pieces annually, among 3000 different part numbers. I'm putting together the bi-annual ISO/AS9100 management review presentation, and looking to make the case to do more SPC on the floor.

We've got an internal goal of 20,000 PPM, which is # of parts rejected in inspection vs # of parts accepted.

External customer goal is 500ppm (part escapes vs parts shipped).

I'm not sure it's realistic to achieve a 40x reduction in PPM through sampling at final. Is there a statistical way of proving this?

If you know your incoming ppm and your sample AQL (say 2.5% AQL), can you show statistically how many escapes you'd expect?

If someone could point me in the right direction, I'd really appreciate it. I'd love to stop the NCM by addressing the process instead of doing more inspections.

Thanks for the help!

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
you can calculate the Average outgoing quality (AOQL) IF you are doing sampling inspection and then performing 100% inspection after a lot fails.

But this 'precise' result is not very accurate. for it to be accurate you would have to truely randomly sample. there is also some effect of non homogenous defect distribution even when randomly sampling.

One thing to remember is that an AQL plan is intended to ACCEPT lots that have up to the AQL defect rate...

AOQL = y [ 1/(sample size) - 1/(lot size) ]

where y is related to the acceptance number, c.

c y
0 0.368
1 0.841
2 1.372
3 1.946
4 2.544
5 3.174
10 6.535

Predicting COVID-19 Aspects - Pandemic Modeling (Easter 2020) Coffee Break and Water Cooler Discussions 11
E Predicting Machined Components Capability based on Historical Data of Similar Parts Capability, Accuracy and Stability - Processes, Machines, etc. 1
Predicting the Future through 19th Century French Post Cards Coffee Break and Water Cooler Discussions 1
Predicting the outcome using high No Trouble Found Rate Statistical Analysis Tools, Techniques and SPC 4
Using Regression Analysis in Excel - Predicting a Value Statistical Analysis Tools, Techniques and SPC 30
Reliability Prediction - Predicting the Reliability of an Inductor (Semi-conductor) Reliability Analysis - Predictions, Testing and Standards 8
Predicting the Internet in 1995 After Work and Weekend Discussion Topics 0
C Statistical technique sought for predicting replacement of perishable tooling Statistical Analysis Tools, Techniques and SPC 14
External Audit and Certificate prorogation due to the pandemic General Auditing Discussions 10
Audit non-compliance API Q1 - Use of External Documents 4.4.4 in Product Realization Oil and Gas Industry Standards and Regulations 5
510(k) for a control kit for an external IVD test kit 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 1
Is it required to have an SOP for external audits? Medical Device and FDA Regulations and Standards News 7
External Standards and Regulations Management Process Document Control Systems, Procedures, Forms and Templates 10
What kind of wine best complements the Friday that you close out your external audit findings? Opinions are welcome. Coffee Break and Water Cooler Discussions 12
How to apply external voltage to SIP/SOP IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
Qualifying commercial off the shelf (COTS) external suppliers ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 10
Internal and external auditor competency to CSR's IATF 16949 - Automotive Quality Systems Standard 20
IATF 16949:2016 7.1.5.3.2 External Laboratory - How to approve the Testing Laboratory without accreditation scope IATF 16949 - Automotive Quality Systems Standard 2
OHSAS 18001 external auditor finding personal interpretation? Occupational Health & Safety Management Standards 5
External power supplies: How close does the safety report have to match the end-use application? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
Reduction of software class based on multiple external risk controls IEC 62304 - Medical Device Software Life Cycle Processes 5
Identifying and Controlling External Documents Document Control Systems, Procedures, Forms and Templates 3
External Laboratories and OEM Calibration IATF 16949 - Automotive Quality Systems Standard 0
AS9120B flow down to external providers: Records Retention AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 2
IATF 16949 7.1.5.3.2 External Laboratory - On Site Calibration IATF 16949 - Automotive Quality Systems Standard 8
Using external FDA and ISO 13485 audit as internal audit Internal Auditing 6
ISO 17025 2017, Requirement 6.6.3 - Communicate requirements to external providers ISO 17025 related Discussions 4
Determining if Maintenance Contractor is an External Service subject to ISO 9001 Clause 8.4 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 43
The Perfect audit? External Audit causes a significant negative impact in a company General Auditing Discussions 9
AS9100D 8.4.1.1 external providers question - Walmart, Home Depot, our lawn care team. etc. AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 20
External Auditor issue with Internal Audits Internal Auditing 7
Do we need to treat local law as external origin documents? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 15
ISO 9001:2015 Clause 8.4.3 "Information for External Providers" buying from online retailers. ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 10
Applicability of Means of Protection, working voltage in an Automated External Defibrillator IEC 60601 - Medical Electrical Equipment Safety Standards Series 0
Necessity of external watchdog next to internal watchdog ISO 14971 - Medical Device Risk Management 1
How to reply NCR on ineffectiveness of corrective action during IATF external audit? This is repeated issue whereby some mistake was done. IATF 16949 - Automotive Quality Systems Standard 7
AS9100 8.4.2 Type and Extent of Control - External provider test reports Manufacturing and Related Processes 24
AS9120B Control of External Providers for Franchised Distribution AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 0
Tools and equipment provided by customer - Considered as external provider? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
Transportation - External Service Provider ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
ISO9001:2015 Clause 9.1 - What the external auditor will look at? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 11
IATF 16949 7.1.5.3.2 External Laboratory - Calibration of Nikon machine in factory IATF 16949 - Automotive Quality Systems Standard 24
External power supply - requirements in safety/EMC test? IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
How to determine the internal and external issues in ISO 45001 standard? Occupational Health & Safety Management Standards 2
How to efficiently and compliantly reference external standards/regulations Other Medical Device Related Standards 2
IATF 16949 7.1.5.3.2 FAQ #7 Audit Finding - External Calibration Laboratory IATF 16949 - Automotive Quality Systems Standard 7
IATF checklist for External Supplier Audit IATF 16949 - Automotive Quality Systems Standard 9
Ignoring a Failed Gage R&R and upcoming external audit IATF 16949 - Automotive Quality Systems Standard 22
IATF 16949 7.1.5.3.2 External Calibration Laboratory Requirelents IATF 16949 - Automotive Quality Systems Standard 15
Risk Approach doesn't address External Issues (Auditor's Comment) ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 30