Understanding control chart and measurement capability

shellig

Starting to get Involved
#1
I thought I had a pretty good handle on this but after trying to explain to others the risks of control charting without practical understanding, I realize I need more help to explain clearly:

1) Thinking about the real values. Is there really a difference to the customer/product/process if the difference is X? Just because the chart tells you that, think about what that means...

2) This is kind of a subset of 1): If you can only measure to half a gram and the control chart range is 3 grams should you be concerned when the measurement is just out of range because of the uncertainty of the measurement?
Where can I find information to better understand this (measurement uncertainty and impact on SPC)?

3) Reacting without using rules, "yes that is the highest value for the year, but within the control chart - normal variation vs. special circumstance." This does not seem to come across when I try to explain it.

I really appreciate your help!
Shelli
 
Elsmar Forum Sponsor

Miner

Forum Moderator
Staff member
Admin
#2
I am not certain what you are asking in question 1.

Regarding your second question, the control limits include the measurement variation. Therefore, a point outside the control limits has exceeded both the common cause variation of the process AND the measurement variation.

For question 3, there is a good illustration by Deming on the impact of "tampering", which is reacting to a process that is still in control, and how this actually increases variation.
 

Bev D

Heretical Statistician
Staff member
Super Moderator
#3
I would add to point 3 to not forget that if your process is 'in control' but still giving you 'bad' results you can and should investigate to understand the cause of all of the ("common cause" variation (as opposed to just one result, aka "assignable cause")


..and clarity around your first question will help us
 
Thread starter Similar threads Forum Replies Date
P Minitab Data Analysis - Understanding if a Process is in Control or Not Using Minitab Software 2
N Understanding, Challenging & Approving Supplier Control Plans FMEA and Control Plans 7
G Understanding Identification of Design in QSR 21 CRF Part 820.30 Design Control (f) 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 2
K Understanding True position - Drawing Feature Control Frames - ANSI Y14.5 Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
C Operator understanding of what Control Plans are and how they are used Document Control Systems, Procedures, Forms and Templates 8
K Understanding Control Charts Methodology for Attributes like Plug Guages. Statistical Analysis Tools, Techniques and SPC 1
M Problems of understanding 4.1 c - Operation and control of processes are effective ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
D Surface Roughness understanding Inspection, Prints (Drawings), Testing, Sampling and Related Topics 1
P Understanding DFMEA and PFMEA - Supplier Related IATF 16949 - Automotive Quality Systems Standard 21
DuncanGibbons Understanding the applicability of Design of Experiments to the IQ OQ PQ qualification approach Reliability Analysis - Predictions, Testing and Standards 0
B Measuring and monitoring equipment - Understanding which procedures to be compliant with ISO 13485 ISO 13485:2016 - Medical Device Quality Management Systems 6
M Informational Health Canada has launched an e-Learning tool to aid in understanding the premarket regulatory requirements for medical devices in Canada Medical Device and FDA Regulations and Standards News 0
S Understanding UDI requirements - Class 2 medical device (hearing aids) 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 3
M Informational Understanding Costs And Risks For HFE Usability Studies — Part 1: Testing In-House Medical Device and FDA Regulations and Standards News 0
P Understanding FDA draft "Management of Cybersecurity in Medical Devices" Medical Information Technology, Medical Software and Health Informatics 3
J Properly understanding SPC - Newbie SPC questions Statistical Analysis Tools, Techniques and SPC 29
R Understanding a few points on ISO 9001's Design and Development Planning ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 1
Z Understanding Cycle Time - Why the time of the other activities are left out Lean in Manufacturing and Service Industries 11
J Understanding ISO 9001:2015 - 10.3 Continual Improvement ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 10
J Understanding ISO9001:2015 - 8.3: Design and Development of Products and Services ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 3
E Root Cause Analysis - Is Insufficient Understanding an acceptable Root Cause? General Auditing Discussions 9
E Understanding of TS 16949 Clause 7.6.2 IATF 16949 - Automotive Quality Systems Standard 5
K Understanding IEC 60601-2-68 requirements ISO 13485:2016 - Medical Device Quality Management Systems 1
A Training material for interpretation & understanding Part 11 requirements 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 2
N Understanding the absolute uncertainty specification for a Fluke 5500A Measurement Uncertainty (MU) 3
M Definition Recommendations - Understanding "recommendations" and "recommended corrective action" Definitions, Acronyms, Abbreviations and Interpretations Listed Alphabetically 8
S Understanding UDI (Unique Device Identification) Other US Medical Device Regulations 10
T Understanding USP <1112> Water Activity as applicable to Medical Devices Other Medical Device and Orthopedic Related Topics 4
K Understanding Risk Management Requirements according to AS9100 AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 11
S MIL-HDBK-217 - Understanding the various Environmental Conditions Reliability Analysis - Predictions, Testing and Standards 1
D What is your understanding or interpretation of TS16949 7.4.1.2 IATF 16949 - Automotive Quality Systems Standard 6
C Understanding the relationship between 62304 and the MDD ER IEC 62304 - Medical Device Software Life Cycle Processes 7
S Understanding Subgroup Size - Multi Cavity (Minitab) Statistical Analysis Tools, Techniques and SPC 4
R Understanding clause 15.4.2.1 d) of amendment 1:2012? IEC 60601 - Medical Electrical Equipment Safety Standards Series 7
M Understanding accreditation, MoUs, certifications Other ISO and International Standards and European Regulations 28
L Mobile Medical App - Understanding 21 CFR Part 820 Requirements 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 3
D Understanding and implementing ISO 17025 ISO 17025 related Discussions 9
M Understanding Versions of Collateral and Particular Standards IEC 60601 - Medical Electrical Equipment Safety Standards Series 7
S Understanding, Analysis and Monitoring Quality Defects on Composite Components Statistical Analysis Tools, Techniques and SPC 3
S Understanding PMS (Post Market Surveillance) and PMCF (Vigilance and PMCF) Quality Manager and Management Related Issues 1
B Understanding why my CpK and PpK are low, and LCL Statistical Analysis Tools, Techniques and SPC 20
S Understanding Quality Objectives, Metrics and KPI ISO 13485:2016 - Medical Device Quality Management Systems 15
Q Beginner's Understanding - The Purpose and Applications of QMS/ISO Standards Philosophy, Gurus, Innovation and Evolution 12
Q Understanding Configuration Management AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 16
W Understanding PPAP Appearance Approval APQP and PPAP 22
V Understanding Automotive Coating for Seating Mechanism Components Manufacturing and Related Processes 1
M Understanding of Regression and ANOVA in Minitab Statistical Analysis Tools, Techniques and SPC 8
4 Understanding ILAC policy P14:12/2010 6.3 part a) General Measurement Device and Calibration Topics 28
H Understanding 8.2.3 M&M of Processes for our Internal Audit ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 6
P Understanding ISO 26262 Road Vehicle Functional Safety Other ISO and International Standards and European Regulations 2

Similar threads

Top Bottom