# Interpretation of DOE interaction plot

D

#### debun

I don't do DOE's often/ever and wanted some help interpreting my results. I have concluded the following

a) Power/Seal time and Power/Shim height have no interactions. the rest do.

Here are my questions.
1) How can I rank the strength of the interactions? So far I would say
Pre Seal/Seal then a close call between Pre seal/Shim & Seal/Shim
and last Power/Pre Seal. Is this correct? Is there some metric in Minitab I can use to rank the interactions?

2) Does the position of the cross or the fact that they don't cross have any weight on the strength of the interaction? For example Pre seal/Shim & Seal/Shim. Pre seal/Shim crosses close to the -1 but Seal/Shim doesn't cross at all. Do you just look at the difference in slope?

3) Is there an idiots guide to DOE interpretation?

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
a) Power/Seal time and Power/Shim height have no interactions. the rest do.
I'd be very careful about this. just because the mean connectors aren't parallel doesn't mean that an interaction actually exists. It could simply be sampling error of the mean. the p value should help with this, but the REAL test is to plot the individual values about the means. remember statistical significance doesn't mean practical importance.
Here are my questions.
1) How can I rank the strength of the interactions? So far I would say
Pre Seal/Seal then a close call between Pre seal/Shim & Seal/Shim
and last Power/Pre Seal. Is this correct? Is there some metric in Minitab I can use to rank the interactions?
2) Does the position of the cross or the fact that they don't cross have any weight on the strength of the interaction? For example Pre seal/Shim & Seal/Shim. Pre seal/Shim crosses close to the -1 but Seal/Shim doesn't cross at all. Do you just look at the difference in slope?
where they cross is irrelevant. the most common interactions across industry are those that look like < or > and not X...

#### Miner

##### Forum Moderator
Staff member
2) Does the position of the cross or the fact that they don't cross have any weight on the strength of the interaction? For example Pre seal/Shim & Seal/Shim. Pre seal/Shim crosses close to the -1 but Seal/Shim doesn't cross at all. Do you just look at the difference in slope?

3) Is there an idiots guide to DOE interpretation?
2) Converging lines will eventually cross. It just happens outside of your experimental design space.

3) While not an Idiot's Guide, this is a decent overview. Another from Minitab.

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
Miner (or Statistical Steven if you are out there): I seem to vaguely recall that there are two types of interactions: the one where the detail looks like X and the one where it looks like: /. I believe they had names? I can't find the reference right now. Some X interactions will look like / in a constrained design space, but some / interactions will never cross (X) because they are physically different types of mechanisms...

#### Statistical Steven

##### Statistician
Staff member
Super Moderator
Miner (or Statistical Steven if you are out there): I seem to vaguely recall that there are two types of interactions: the one where the detail looks like X and the one where it looks like: /. I believe they had names? I can't find the reference right now. Some X interactions will look like / in a constrained design space, but some / interactions will never cross (X) because they are physically different types of mechanisms...
Hey Bev, sorry I missed connecting with you again after your talk at WCQI. I am not familiar with different names for the interaction plot patterns, though your point is spot on about looking at the individual values and see how the different runs impact the interaction!

#### Miner

##### Forum Moderator
Staff member
BevD

Do you mean qualitative vs. quantitative? Qualitative interactions are those that change slope and direction, while quantitative interactions change slope, but not direction.

You can also have interactions between continuous variables as well as between continuous/discrete variables.

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
Miner - THANK YOU! that's exactly what I was thinking of...I need to 5S my brain...

D

#### debun

Lots of good info in here. I was able to use the minitab help and they have a good write up on interpreting the results. The pretty pictures are cool but the p values are where the real info is.

#### Bev D

##### Heretical Statistician
Staff member
Super Moderator
A plot with individual values will beat a p value every day. From a stats standpoint all the value is in the adjusted r square number...

Contingency plan - IATF Sanctioned Interpretation 17 IATF 16949 - Automotive Quality Systems Standard 4
MDD Article 12/ MDr Article 22 interpretation EU Medical Device Regulations 2
MDR, Annex I, 23.1 Interpretation - IFU on the website EU Medical Device Regulations 5
MDR Article 22 Interpretation EU Medical Device Regulations 3
Interpretation of the MDR GSPR 23.4 (u) EU Medical Device Regulations 2
IATF16949 - Interpretation of Customer Requirements clauses IATF 16949 - Automotive Quality Systems Standard 3
Interpretation of GMP Requirements for class 1 medical device manufacturer (device GMP exempt, only General controls applicable) 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 4
MDR Rule 10 interpretation - Active Device EU Medical Device Regulations 6
% Study variation low, % tolerance high - GR&R Interpretation help Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 3
Interpretation with regards to Ppk > Cpk Capability, Accuracy and Stability - Processes, Machines, etc. 14
OHSAS 18001 external auditor finding personal interpretation? Occupational Health & Safety Management Standards 5
OEM branding - My interpretation of the LVD Directive makes us a manufacturer CE Marking (Conformité Européene) / CB Scheme 3
Average Peel Strength - Interpretation of BS EN 868-5:2018 and ASTM F0088/F0088M Other Medical Device Related Standards 2
ISO 50001 Interpretation of section 3.3.9 (Outsourcing) ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
Interpretation of significant change - material change Canada Medical Device Regulations 3
MDR Software Rule 11 Formal Interpretation EU Medical Device Regulations 7
IATF Sanctioned Interpretation No. 7 - Type and Extent of Control (supplemental) IATF 16949 - Automotive Quality Systems Standard 4
Interpretation of MDR 2017/745 Article 23 - CE Mark Requirements EU Medical Device Regulations 8
Hand-Held dosing device has no PATIENT - Interpretation of the PATIENT definition IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
G Medical Device "Immediate Container" Interpretation of Definition US Food and Drug Administration (FDA) 2
A Interpretation of Article 16 (2b) - Packaging, samples and Certificate EU Medical Device Regulations 10
EU MDR Corrigendum Interpretation EU Medical Device Regulations 3
Informational MDCG 2019-3 Interpretation of Article 54(2)b – Pre- market clinical evaluation consultation procedure with the involvement of expert panels Medical Device and FDA Regulations and Standards News 0
G EU MDR 2017/745 Rule 11 interpretation - Re-classification of a Software as Medical Device Other Medical Device Related Standards 0
Interpretation of Clause 5.5.2 in ISO 13485:2016 ISO 13485:2016 - Medical Device Quality Management Systems 2
P x I = Value interpretation for residual risk? ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 1
T CSA Z299.3-85 Nuclear interpretation AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 2
D VDA Trigger Matrix in the VDA 6.2 Manual - Interpretation and Use VDA Standards - Germany's Automotive Standards 3
Interpretation of Customer Specific Requirements of Continental - Records Retention Customer and Company Specific Requirements 6
S Interpretation or Definition of ‘Once Every 5 Days’ ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
N What is the interpretation I-MR-R chart in this question? Statistical Analysis Tools, Techniques and SPC 1
ME (Medical Equipment) Systems - IEC 60601-1 Clause 16.1 Interpretation IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
IATF 16949 Cl. 7.1.5.2.1 "Calibration/Verification Records" Interpretation IATF 16949 - Automotive Quality Systems Standard 12
Clarification on interpretation of some EN ISO 14971:2012 & IEC 62304:2006 req's ISO 14971 - Medical Device Risk Management 46
IATF 16949 - 7.1.3.1 Plant, Facility, and Equipment Planning - Interpretation IATF 16949 - Automotive Quality Systems Standard 8
R Location Interpretation on Drawing - Hole to Hole? Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
T TS 16949 Clause 7.4.1.2 and Sanctioned Interpretation IATF 16949 - Automotive Quality Systems Standard 12
Interpretation of new IAQG ruling - Audit duration for nonconformance verification AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 7
K Interpretation of IEC 60601-1-2 Electromagnetic Compatibility – Requirements & tests IEC 60601 - Medical Electrical Equipment Safety Standards Series 4
S Heat Treatment - Soaking time interpretation Manufacturing and Related Processes 5
Training material for interpretation & understanding Part 11 requirements 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 2
Interpretation of "Any or All"'? IEC 60601 - Medical Electrical Equipment Safety Standards Series 10
G Interpretation of phrase - "Direct Authority" EASA and JAA Aviation Standards and Requirements 5
Brazil: Interpretation of RDC 185 Other Medical Device Regulations World-Wide 6
D What is your understanding or interpretation of TS16949 7.4.1.2 IATF 16949 - Automotive Quality Systems Standard 6
M Interpretation of Plus/Minus Draft - Injection Molded Parts Inspection, Prints (Drawings), Testing, Sampling and Related Topics 10
E FDA Significant Change Interpretation - Guidance Document EU Medical Device Regulations 2
ISO 9001:2008 interpretation not the same per country? (Netherlands and France) ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
M Multiple Standard Interpretation Queries Occupational Health & Safety Management Standards 4
A Need MSA %GRR Interpretation Advice Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2