# Non parametric test for semi-quantitative data.

#### statistiques1992

##### Registered
Hi everyone, I have a question about the sample size for paired comparison test. I want to compare multiple measurements from 2 machines, in order to demonstrate that there is no significant difference between these 2. Each day I can run these 2 machines in the same condition, so for each day I will have a pair of data from these 2 machines.

1. The first measurement I want to test is a semi-quantitative measurement, which have a limit of quantification (below that limit, the machine is not capable to give the exact result). Historically, we have around 13 data, which are all below this limit. For the testing, I want to consider this limit our acceptance criteria. But I don't know how many runs minimum I need to have.

2. The second measurement I want to test is a count data. Since we don't have a acceptance criteria, I am thinking about a non-parametric test for paired data. In that case, how many runs minimum I need to have?

Thanks for the help.
S.

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
If you run the machines at the same time using the sample batches of material (split the materials) adn if you randomly mix the operators between machines, you will only need to run the machines for 5 days, using all of the results for each machine each day. Then if all 5 of 1 machine’s results are better than all 5 of the results of the other machine then you will have an alpha of 5% that the machines are different from each other (subject to any othet confounding). This is a matched pair parametric test that use simple probability. It is like flipping a coin 5 times in a row and getting 5 heads. (Or 5 tails). It will work for all kinds of data.

We would need more details to give a more detailed answer...

#### statistiques1992

##### Registered
If you run the machines at the same time using the sample batches of material (split the materials) adn if you randomly mix the operators between machines, you will only need to run the machines for 5 days, using all of the results for each machine each day. Then if all 5 of 1 machine’s results are better than all 5 of the results of the other machine then you will have an alpha of 5% that the machines are different from each other (subject to any othet confounding). This is a matched pair parametric test that use simple probability. It is like flipping a coin 5 times in a row and getting 5 heads. (Or 5 tails). It will work for all kinds of data.

We would need more details to give a more detailed answer...
Thanks Bev D for the answer. I see your point here, so we consider that for each run, one machine has 50% chance of getting a better result than the other one (if we suppose that the 2 machines are similar). The fact that all my data are below the limit of quantification can be a problem? (some null results and some positive results w/o the exact value).
For each day, the 2 machines will be run by the same operator in the same condition, in short interval of time. What details do you need to give a more detailed answer? Sorry I am not yet familiar with all this.

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
If one of your characteristics is so low that you only get zeros or a result below the limit of detection, why are you concerned if the machines are different on this characteristic? The test will tell you if there is a difference or if there isn’t...we never do a comparison test to prove one answer or the other we do it to know which answer is true.

#### Steve Prevette

##### Deming Disciple
Staff member
Super Moderator
2. The second measurement I want to test is a count data. Since we don't have a acceptance criteria, I am thinking about a non-parametric test for paired data. In that case, how many runs minimum I need to have?

Not having an acceptance criteria doesn't mean you need to shift to non-parametric tests. By the way, a good "guesstimate" for sample size is 25, given no other information.

Thread starter Similar threads Forum Replies Date
A "good" non-parametric test summary? Statistical Analysis Tools, Techniques and SPC 0
A Cnpk (Non-Parametric Capability Analysis) to assess whether the Process is Stable Capability, Accuracy and Stability - Processes, Machines, etc. 7
Use of Non-Parametric Statistics and Non-Normal Data Statistical Analysis Tools, Techniques and SPC 33
Water requirement for Non-sterile topical OTCs Pharmaceuticals (21 CFR Part 210, 21 CFR Part 211 and related Regulations) 0
Procedure packs with non-medical devices EU Medical Device Regulations 1
Non Sterile Medical Device Environmental Tests Other Medical Device Related Standards 4
Advice on how to reduce overhead of handling non-conforming material Nonconformance and Corrective Action 7
Team to analyze a non conformance Customer Complaints 26
Promoting and marketing of a non approved device 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 4
0 non conformities in registrar audits over 4 years Management Review Meetings and related Processes 12
CE Marking Class 1 (Non sterile) medical device CE Marking (Conformité Européene) / CB Scheme 3
Supplier requirements - Major supplier is a Non-Profit registered with ICCBBA (FDA UDI) Supply Chain Security Management Systems 12
Free Sales Certificate for Non Medical Devices Other Medical Device Related Standards 2
Ppk results shown as asterisk after the transformation of Non-normal data Using Minitab Software 4
When is necessary to have RoHS declaration on non-electrical parts? REACH and RoHS Conversations 1
Non Aerospace topics - Anything for military trucks, trailers, Humvee type vehicles? AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 8
Dealing with non conformity caused by Supplier Components detected in the production line IATF 16949 - Automotive Quality Systems Standard 14
Who are the go to companies for non-destructive hardness testing? General Measurement Device and Calibration Topics 3
Non conformance (NC) or Corrective & Preventive action (CAPA) CE Marking (Conformité Européene) / CB Scheme 7
How does IEC-60601-1 apply to a non-medical device in the patient vicinity? IEC 60601 - Medical Electrical Equipment Safety Standards Series 1
FDA guidance on non-sterile Medical Device Packaging Medical Device and FDA Regulations and Standards News 7
Qualification for non gmp service providers Supplier Quality Assurance and other Supplier Issues 1
MDD x PPE Directive - Statement of Non-Applicability EU Medical Device Regulations 3
Exclusions or justification for non-applicability of IEC standards Reliability Analysis - Predictions, Testing and Standards 1
Non-EU Language Requirements Other Medical Device Regulations World-Wide 3
Non-Conformances Found After 3rd Party Sorting Supplier Quality Assurance and other Supplier Issues 12
ISO 13485 8.3 - Non-Conforming Materials - on-line rework or part of process? ISO 13485:2016 - Medical Device Quality Management Systems 11
Audit non-compliance API Q1 - Use of External Documents 4.4.4 in Product Realization Oil and Gas Industry Standards and Regulations 8
Using non-conforming components even though the final assembly is conforming? Manufacturing and Related Processes 5
Competent Authority notification for non-EU manufacturer EU Medical Device Regulations 4
CE marking for NON-EU EU Medical Device Regulations 0
Non-GMP examples in Pharmaceutical industry Pharmaceuticals (21 CFR Part 210, 21 CFR Part 211 and related Regulations) 2
Increasing PFMEA occurrence ranking after non-conformance FMEA and Control Plans 4
Non-Conformance and Deviations ISO 13485:2016 - Medical Device Quality Management Systems 4
Risk Assessment Checklist for Non product Software IEC 62304 - Medical Device Software Life Cycle Processes 1
Ideas for developing a Supplier Quality Management System, non automotive ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
Audit non-compliance - API Spec Q1 9th Ed 5.6.1.2 b Oil and Gas Industry Standards and Regulations 10
Applicability of new non-harmonized standards (MDD/MDR) EU Medical Device Regulations 14
Scope of Combined ISO 9001 and IATF 16949 QMS - Non-automotive customers ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
Guidance on manufacturing non-surgical face masks US Food and Drug Administration (FDA) 3
Do non-IATF customers need to be included in audit scope? IATF 16949 - Automotive Quality Systems Standard 23
If it doesn't prevent a non-conformance, is it a preventive action? IATF 16949 - Automotive Quality Systems Standard 13
Addressing Non-Conformances from an Internal Audit that are not product related ISO 13485:2016 - Medical Device Quality Management Systems 11
Non conformance product identification and traceability 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 4
Non-Conformance vs OFI -- your best descriptions ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 61
Question about Non-conformances during New Product Introduction Nonconformance and Corrective Action 14
Bioburden monitoring for surgical instrument provided non-sterile EU Medical Device Regulations 3
Packaging validation for non-sterile Medical Equipment Other Medical Device Related Standards 1
Can we provide training plan as corrective action for IATF 16949 Non conformity? IATF 16949 - Automotive Quality Systems Standard 9
Medical System with non-medical device and FCC US Food and Drug Administration (FDA) 5