Choosing number of subgroups and subgroup size

B

bunnath

#1
Hi all,

need help choosing the subgroup number and size of a particular process I would like to monitor.

the process has 12 different fixtures that are simultaneously used during the day. There are about 3 process events per day for each fixture. I would like to monitor one of the outputs and show the within fixture variation, and also detect any trends and the stability of the process.

What is the best way to do this?

Thanks in advance,
Bunnath
 
Last edited by a moderator:
Elsmar Forum Sponsor

Scott Catron

True Artisan
Super Moderator
#2
Just a bump to see if anyone can help with this.

bunnath, I'm no SPC guru, so I'm not sure I understand what you mean by subgroup.

Also, do you have current SPC data for the processes you describe or are you just starting to collect data?
 
D

Duke Okes

#3
Rather than thinking about SPC subgroups I would think about using a multi-vari chart (a Shainin technique)
 

Jim Wynne

Leader
Admin
#4
Hi all,

need help choosing the subgroup number and size of a particular process I would like to monitor.

the process has 12 different fixtures that are simultaneously used during the day. There are about 3 process events per day for each fixture. I would like to monitor one of the outputs and show the within fixture variation, and also detect any trends and the stability of the process.

What is the best way to do this?

Thanks in advance,
Bunnath
If your process is yielding only three measurements per day, you would probably be best advised to avoid rational subgrouping and just use I/MR (Individuals/Moving Range) charts. You can get more information on I/MR charting from the NIST/Sematech Engineering Statistics site.
 

Bev D

Heretical Statistician
Leader
Super Moderator
#5
Rather than thinking about SPC subgroups I would think about using a multi-vari chart (a Shainin technique)
well, Shainin certainly promoted the multi-vari but it wasn't "his" technique. It was developed by Leonard Seder

That said, this approach is an excellent start for almost any SPC application to determine the important compoennets of variation that will lead you to the most effective subgrouping scheme.

and as always Jim's advice is also very sound.
 
Thread starter Similar threads Forum Replies Date
C Quantifying risk in choosing the number of parts, operators and replicates in a GR&R Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
S Help needed in choosing the method of calculating the minimum sample size Internal Auditing 12
T Choosing a Notified Body for MDR - SGS/BSI/DNV/DQS-MED Registrars and Notified Bodies 0
E Choosing correct MOPs IEC 60601 - Medical Electrical Equipment Safety Standards Series 2
Q Choosing Nonconformities to Report ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 26
Q Old products new class - Dental Devices - Choosing tests EU Medical Device Regulations 2
M Choosing Auditors - ISO 9001 / ISO 27001 (UK) IEC 27001 - Information Security Management Systems (ISMS) 2
T AS9100D - Scope of QMS for New Company - Only Choosing a Function Subset Due to Management AS9100, IAQG, NADCAP and Aerospace related Standards and Requirements 14
E Choosing an ISO 9001 registrar with auditors familiar with our industry Registrars and Notified Bodies 10
M Dilemma about choosing the most applicable clause related to Risk ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 19
J Choosing QMS Software for Aerospace Company Quality Assurance and Compliance Software Tools and Solutions 5
B Choosing not to calibrate (IATF 16949) IATF 16949 - Automotive Quality Systems Standard 6
Q Choosing between ISO 9001 (2015) & TL 9000 certifications ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
H On choosing touchscreen displays and ensuring IEC 60601 compliance IEC 60601 - Medical Electrical Equipment Safety Standards Series 6
Q Choosing In-Process Inspection Characteristics Inspection, Prints (Drawings), Testing, Sampling and Related Topics 7
L Choosing the correct Distribution for Acceptance Sampling Inspection, Prints (Drawings), Testing, Sampling and Related Topics 19
S Choosing a suitable type of Elisa to Test my Sample Misc. Quality Assurance and Business Systems Related Topics 3
S Choosing the correct Elisa Test Food Safety - ISO 22000, HACCP (21 CFR 120) 1
K Choosing a Six Sigma training organization Six Sigma 4
H Choosing between RABQSA Lead Auditor or ASQ CQA Certification Professional Certifications and Degrees 2
S Choosing ISO 9001 Training and if I need the training for work ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 8
S CE Marking choosing between module A, B CE Marking (Conformité Européene) / CB Scheme 2
A Getting Stuck Choosing a Sampling Plan Inspection, Prints (Drawings), Testing, Sampling and Related Topics 6
M Choosing the right Industry Financial Report Manufacturing and Related Processes 1
M Advice for choosing Rechargeable Lithium Batteries to be used in a Medical Device Other Medical Device Related Standards 16
L Choosing a Statistical Test for dissertation results! Statistical Analysis Tools, Techniques and SPC 4
I Choosing a X-Ray Fluorescence Measuring Device for Chrome Coating Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
J Choosing the Best Standard - ISO 9001 or ISO 13485 ISO 13485:2016 - Medical Device Quality Management Systems 14
B Choosing Inspection Level and AQL AQL - Acceptable Quality Level 1
I Choosing the alpha level in an ANOVA Study Statistical Analysis Tools, Techniques and SPC 3
M Tolerance vs. Study Variation - Choosing the right one Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 5
S Choosing a Higher EER Air Conditioner After Work and Weekend Discussion Topics 7
T Choosing a Mentor Career and Occupation Discussions 3
K Selection Criteria for choosing a Management Representative for QMS ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 13
A Choosing Document Control Software Document Control Systems, Procedures, Forms and Templates 13
S Choosing Parts for Attribute MSA (Measurement System Analysis) in 4th Edition, pg 132 Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 2
C Difference between softwares in choosing correct Taguchi designs Using Minitab Software 16
bio_subbu Choosing a laboratory for biocompatibility test ISO 13485:2016 - Medical Device Quality Management Systems 8
M Choosing a Laser Micrometer - Your recommendations? General Measurement Device and Calibration Topics 8
G Short TQM training - Choosing of most important points Training - Internal, External, Online and Distance Learning 3
D Choosing a Vision System - Recommendations for a User Friendlier System Quality Tools, Improvement and Analysis 3
D Need Help on choosing dimensional standards / equipment General Measurement Device and Calibration Topics 2
J Choosing Samples for Gage R&R - Randomly picked samples show very little variation Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 13
Tim Folkerts DOE: Choosing a Design - Factors that affect the choice of design The Reading Room 0
B ISO10012:2003 Question - Choosing or assessing the capability of a piece of equipment Other ISO and International Standards and European Regulations 1
G Choosing a Sampling plan for Start Up Fabless IC Company - Guarantee a 200 DPM limit Inspection, Prints (Drawings), Testing, Sampling and Related Topics 9
gard2372 Choosing between a Small Company or a Large Company Career and Occupation Discussions 17
D Choosing a notified body for a new start up company in the UK - Medical Device area Registrars and Notified Bodies 6
G Choosing Supplier Evaluation Methods - Determining what a Critical Supplier is Supplier Quality Assurance and other Supplier Issues 31
Steve Prevette Choosing Performance Indicators Registered Visitor Articles Archive 0

Similar threads

Top Bottom