Interpreting Span Measurement - P95-P5

patkim

Registered Visitor
#1
Back in 2002-2003 I was working with a company which was one of the vendors to General Electric (GE).
GE with its strong focus on Six Sigma, we were literally bombarded with Six Sigma knowledge. Now I am retracing my steps and I have some queries about a Metric called Span that GE has been using to assess On Time Delivery Performance. Unfortunately very little info is available on the internet about Span. My very little knowledge about Span has only added to my confusion.

Span is a measure of dispersion, Defined as P95-P5. Span removes the extreme outliers of your process by looking only at the difference between the 95th and 5th percentiles.
GE Used (and may still be using) Span to assess on time delivery performance.

If I correctly understand, lower the Span better the performance?
However I guess Span can be totally misleading in case of Normal data.
e.g. all my deliveries are late by 3 days. Now my variation from target is 3 every time so P95 is also 3 & P5 is also 3. Span is 0 but I was late every time resulting into huge customer dissatisfaction.

So how do you really interpret Span? Can someone help? If I have a few early deliveries by -2 days and few late deliveries by +4 days and say Span is 3 what does it practically mean?

In a six sigma project to improve Span, is Span data translated to Sigma Value? Is so how?

Thanks.
 
Elsmar Forum Sponsor

Miner

Forum Moderator
Staff member
Admin
#2
Span is a measure of dispersion (i.e., variation), not of location (i.e., mean).

The concept is based on the theory that customers are impacted to a greater extent by unpredictability than they are by consistently "poor" service. In your case, the customer may not be pleased by your 3 days late delivery, but if they know that you are 3 days late 95% of the time, they can plan for that and the impact is minimal. On the other hand, you might average 0 days late yet vary from 3 days early to 3 days late. Your customer cannot plan with that amount of variation.

With Span, the idea is to minimize the dispersion first (maximize predictability) then work on hitting the target. It appears that you already have a Span that has been minimized, so your next step would be to shift the average closer to zero.

You could convert Span plus mean to a sigma value, but I don't recommend it. It would reduce the usefulness of the metric and divert attention away from what is important.
 
Thread starter Similar threads Forum Replies Date
Q Interpreting China Medical Device regulations/standards China Medical Device Regulations 1
P ISO 80369-7 standard - Interpreting which Parts should be in scope Other Medical Device Related Standards 7
K PACS - interpreting MDD and Borderline Guidance CE Marking (Conformité Européene) / CB Scheme 5
M List of Packaging Contents - Medical Devices - Interpreting EU Directive 93/42/EEC CE Marking (Conformité Européene) / CB Scheme 3
D Interpreting Normal vs Weibull Capabilities Capability, Accuracy and Stability - Processes, Machines, etc. 4
B Interpreting Deviations 5 & 6 in Annex ZA in ISO 14971:2012 ISO 14971 - Medical Device Risk Management 1
B Interpreting "misuse" when assessing Hazardous Situations ISO 14971 - Medical Device Risk Management 2
SteveK Interpreting clause 4.1.5 in ISO 13485:2016 ISO 13485:2016 - Medical Device Quality Management Systems 9
M Interpreting Process Controls - 21 CFR Part 820.70(a) 21 CFR Part 820 - US FDA Quality System Regulations (QSR) 5
M Help interpreting 21 CFR Part 806 (corrections and removals) Other US Medical Device Regulations 1
G Interpreting Type 1 MSA (Measurement Systems Analysis) Results Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
M Help interpreting MIL-STD-105E Single Sampling Plans Tables Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
M Biocompatibility in Respiratory Products - Help interpreting whitepaper IEC 60601 - Medical Electrical Equipment Safety Standards Series 22
I Interpreting Product Realization (Clause 7) in ISO 9001:2008 for Service Industry ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 5
V GD&T Interpreting Datums in Two Single Segmented Position Tolerances Inspection, Prints (Drawings), Testing, Sampling and Related Topics 5
M Interpreting X bar and R Control Charts Statistical Analysis Tools, Techniques and SPC 2
B Help with interpreting stock market terminologies Coffee Break and Water Cooler Discussions 4
V Interpreting Zinc Plating Specification GMW 3044 - 6K96/48 APQP and PPAP 2
K Interpreting and Applying 7.3.2 Design and Development Inputs ISO 9000, ISO 9001, and ISO 9004 Quality Management Systems Standards 4
S Interpreting the Calibration Report for my Dial Indicator General Measurement Device and Calibration Topics 3
J Interpreting Process Capability results and ratios Capability, Accuracy and Stability - Processes, Machines, etc. 1
B Length Measure - Interpreting Calibration Results and Measurement Uncertainty (MU) Measurement Uncertainty (MU) 3
S Interpreting Level of Confidence - Round Robin for Tensile Testing - Help needed Statistical Analysis Tools, Techniques and SPC 4
M Interpreting AS9100 Clause 8.2.2 Internal Audit Requirements Internal Auditing 28
T Interpreting my t test in Minitab Using Minitab Software 2
S Interpreting Linear Regression Results from Minitab Using Minitab Software 15
optomist1 Interpreting LMC for Pattern of Slots (GD&T) Inspection, Prints (Drawings), Testing, Sampling and Related Topics 3
optomist1 Interpreting Minitab Test For Equal Variances Using Minitab Software 3
V Interpreting Minitab Gauge R&R Results Using Minitab Software 6
A ISO 2081 - Interpreting Coating Thickness Other ISO and International Standards and European Regulations 3
L Interpreting Injection Molding Tooling Documents - Cavities Manufacturing and Related Processes 3
C Interpreting Gage R&R Results - 3 operators, 3 iterations and 10 parts Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 6
M Interpreting Measurement Uncertainty for Temperature PRT probes Measurement Uncertainty (MU) 2
N Interpreting Hygrometer Calibration Uncertainty - Temperature Coefficient Measurement Uncertainty (MU) 1
mr500 Interpreting Decimals in the mm state - Off Wall Question Inspection, Prints (Drawings), Testing, Sampling and Related Topics 14
J Interpreting clause 7.5.2.1 (validation of software used in production & service) ISO 13485:2016 - Medical Device Quality Management Systems 2
E Interpreting Partial Least Square Results Using Minitab Software 1
C Interpreting Outside Laboratory Calibration Certificate Measurement Uncertainty (MU) 3
M Interpreting MIL-PRF-19500 (Performance Spec, Semicon Dev) - What is LTPD of 20 - ??? Manufacturing and Related Processes 4
T Rules for interpreting control charts Statistical Analysis Tools, Techniques and SPC 2
Q Interpreting Responsibility and Authority Clause 5.5.1 ISO 13485 ISO 13485:2016 - Medical Device Quality Management Systems 18
H Interpreting 'Evaluation of compliance' in ISO 14001 Internal Auditing 4
P Micrometer Gage R&R study - Interpreting the data and suggestions Gage R&R (GR&R) and MSA (Measurement Systems Analysis) 4
W Interpreting a Normal Probability Plot Statistical Analysis Tools, Techniques and SPC 4
Wes Bucey "Downsizing" ramifications - Evaluating and Interpreting the News World News 0
Q Interpreting calibration result of Air Particle Counter on Counting efficiency General Measurement Device and Calibration Topics 1
A Particle Counter Results - Interpreting Data for a Class 100,000 Cleanroom Other Medical Device Related Standards 12
M GD&T Q&A session - Interpreting FCF (Feature Control Frame) Inspection, Prints (Drawings), Testing, Sampling and Related Topics 43
N TL 9000 - Help Interpreting Normalization Unit for Measurements TL 9000 Telecommunications Standard and QuEST 2
K Question on Cp index - Calculating and Interpreting Cp and Cpl. Statistical Analysis Tools, Techniques and SPC 6

Similar threads

Top Bottom