A Balanced view of statistical tests

John Predmore

Trusted Information Resource
#1
Many years ago, I discovered what I consider the Grand Unification Theorem of Statistical Tests, which demystified statistics for me. Most statistical tests, including GR&R, SPC, DOE, T-test, weigh the variation between subgroups against what you would expect, from variation within subgroups. I use the mental image of a scale balance, with sources of within-subgroup variation on one side and between-subgroup variation on the other. The only way to conclude there is a difference is if you see the between-group side is significantly heavier than the within-group side. ANOVA and regression are like a balance with multiple pans, but that is harder to visualize.

I will use Gage R&R as an example. A GR&R is a designed experiment in the way you set up the experiment. The mathematics is the same either way; what matters is which sources of variation are lumped on the right side of the scale and which on the left. If you structure your GR&R with subgroups of Operator A versus Operator B, then reproducibility measures inter-operator variability. In an automatic operation situation, you could compare Equipment type A versus Equipment type B, or method A versus method B, then in one sense, reproducibility compares A versus B, even if there are no human operators. If you mark the parts and place them in the device in the same exact orientation every time, then variation due to orientation is not captured in the analysis. If you allow part placement orientation to vary at random, then within-part variation becomes part of within-group variation. If you purposely control different placement orientations, then within-part variation can be isolated in reproducibility. The mental image of a scale helps me visualize how to organize a statistical experiment.
 
Elsmar Forum Sponsor

Steve Prevette

Deming Disciple
Staff member
Super Moderator
#2
Curious as to the reason for your post . . . Yes, indeed there are mathematical similarities there. I will though repeat what I heard many times from the Deming folks - SPC is NOT a statistical test but an empirical test. There are some folks that have gone way overboard with the Test of Hypothesis model for SPC and then get wrapped around the axle with "is the data normal". And other statements about levels of confidence (similar to the various capability indexes).

Deming vs. Statistical Hypothesis Testing
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1225&context=usgsnpwrc
Enumerative and Analytic Studies « The W. Edwards Deming Institute Blog
 

John Predmore

Trusted Information Resource
#3
@Steve Prevette, My reason is I had a novel thought to share. Years ago, this mental image helped me understand how statistical tests operate. Today, I observe that many users of statistics want to blindly plug in the numbers and have the spreadsheet or Minitab make the decision, but the proper analysis depends greatly on the source of the data and how the experiment is structured. That is the analogy of consciously placing items on one side of the balance or not paying attention. You can take the analogy as far as it provides valuable insights, but stop when it ceases to make sense. All models are wrong, some are useful.
 
Thread starter Similar threads Forum Replies Date
S How to prepare a Balanced Scorecard for QMS & EHS Management system ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
Q Balanced scorecard together with ISO 9001 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 1
AnaMariaVR2 Communicating Strategy with the Balanced Scorecard Business Continuity & Resiliency Planning (BCRP) 0
6 SHEQ/Quality Systems Coordinator Balanced Scorecard Template wanted Quality Tools, Improvement and Analysis 5
P Balanced Scorecard in Measurement of an Experimental Approach Quality Tools, Improvement and Analysis 2
B Has anyone developed an OHSAS 18001 Safety Management System Balanced Scorecard? Occupational Health & Safety Management Standards 13
F ISO 9001, Balanced Scorecard and the EFQM Excellence Model Quality Tools, Improvement and Analysis 3
R Ford BSAQ (Balanced Single Agenda for Quality) System questions Customer and Company Specific Requirements 6
C Balanced Scorecard and KRA (key result area) Quality Manager and Management Related Issues 5
P Minitab error response: "Design is not balanced; execution aborted" Using Minitab Software 4
Q Quality Balanced Scorecard? Example wanted ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 8
S ISO 9001 and Balanced Scorecard ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 7
P Balanced Scorecard Information / Examples Quality Tools, Improvement and Analysis 5
B Benefits of Lean, Lean Six Sigma, Six Sigma, Balanced Scorecard - Making the case Quality Tools, Improvement and Analysis 3
Stijloor Looking for a "Balanced Score Card" training program for small businesses. Training - Internal, External, Online and Distance Learning 5
N Linking BSC (Balanced Score Card) with Six Sigma Six Sigma 18
D Minitab refuses to run saying the Design is Not Balanced - Gage R&R Using Minitab Software 14
A Balanced Scorecard / Strategic Planning linked to Strategical Objectives Misc. Quality Assurance and Business Systems Related Topics 1
A Balanced Scorecard - How to USE Balanced Scorecard? Quality Tools, Improvement and Analysis 15
C Building a Balanced Scorecard The Reading Room 11
L How much do you know about balanced scorecard? Quality Tools, Improvement and Analysis 1
L How long have you known balanced scorecard? Quality Tools, Improvement and Analysis 2
L How is your organization implementing the balanced scorecard Quality Tools, Improvement and Analysis 4
A Balanced Scorecard - Seeking More Information Document Control Systems, Procedures, Forms and Templates 1
S How can Balanced scorecard (a measurement of performance tool) be used in ISO 9001? Quality Tools, Improvement and Analysis 6
J Balanced Score Card - Using this method for performance measurement Quality Tools, Improvement and Analysis 2
A Anybody doing Balanced Scorecards? Quality Tools, Improvement and Analysis 22
S Definition of "worldwide" in view of IATF 16949 and Product conformity IATF 16949 - Automotive Quality Systems Standard 3
Ronen E Interesting Discussion Interesting view of EU Authorised Representative under MDR EU Medical Device Regulations 3
Marc Printable Discussion Thread View Elsmar Xenforo Forum Software Instructions and Help 0
A How to view supplier APQP timeline and do risk management APQP and PPAP 4
T Directors View - Standards like ISO 9001 are "Just a TICK in the BOX" ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
Chennaiite Chaos --> Bird's eye view, simplify & visualize Coffee Break and Water Cooler Discussions 0
S Can I view listed drug products on FDA website similar to listed medical devices? Pharmaceuticals (21 CFR Part 210, 21 CFR Part 211 and related Regulations) 4
N Sponsor asked to view our SOPs remotely using File Sharing Document Control Systems, Procedures, Forms and Templates 1
D Auxiliary View Fold Line convention in ASME standard? Manufacturing and Related Processes 5
Jim Wynne A 1966 View of Home Computers After Work and Weekend Discussion Topics 3
Ajit Basrur How Engineers view things differently :) Funny Stuff - Jokes and Humour 10
Marc Night-Time View of Alexandria, Cairo and the Nile Valley from the NASA Space Station Coffee Break and Water Cooler Discussions 2
S AS9102 for Assembly with Exploded View AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 9
E Orthographic Projection - Which view is correct? Coffee Break and Water Cooler Discussions 4
C Customer Right to View Certification Body Audit Reports? General Auditing Discussions 11
B What do you think about ISO 9001:2008? - Interested in various points of view. ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 24
8 Simulated Factory - Assistance in simulation of a factory with a view to improving it Lean in Manufacturing and Service Industries 3
Sidney Vianna And yet another critical view of ISO 9001:2008 ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 23
T Does EN 60601-1 include 60601-1-2 from a contract point of view IEC 60601 - Medical Electrical Equipment Safety Standards Series 3
kisxena FDA's view on Wiki's for users to find equipment operation procedures 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 14
Q The best way to view standards for free without violating copyright Coffee Break and Water Cooler Discussions 17
G Does anyone have a Contract Review Procedure I can view? Contract Review Process 5
T Johnson Thread View System - Measures many characteristics on a thread plug gage General Measurement Device and Calibration Topics 13

Similar threads

Top Bottom