using spc to make better management decisions
Post on 14-Sep-2014
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DESCRIPTION
In this webinar (sponsored by Gemba Academy), Mark Graban, author of Lean Hospitals, will show how simple statistical process control (SPC) methods can be used by managers and leaders to make better decisions about their businesses. Using examples from manufacturing, healthcare, and services industries, Mark will illustrate the basic SPC rules and will show you how to create and interpret a control chart, allowing you to spot statistically valid trends and avoid overreacting to common cause variation in your performance measures. Please join us for a lively discussion and interactive Q&A! http://www.MarkGraban.com http://www.GembaAcademy.comTRANSCRIPT
Using SPC to Make Better Management Decisions
Mark GrabanAuthor, Lean Hospitals
Co-Author, Healthcare Kaizenwww.MarkGraban.com
@MarkGraban
Key Management Questions• How are we performing?– Are we getting better or worse?
• What action should we take?
“Failure to understand variation is a central problem of management.”
– Dr. Lloyd S. Nelson Some rights reserved by Marco Bellucci
My Most Favorite Book Ever
http://www.spcpress.com/Donald J. Wheeler, PhD
“No data have meaning apart from their context”
Comparisons in the News
1992 1995 1998 2001 2004 2007 20100
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11.21.41.61.8
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Fatalities per 100 Million Vehicle Miles Traveled (U.S. & CT)
U.S.
CT
Need to Look for Trends
“You don't want to make a big conclusion based on just one year.”
– Jonathan Adkins of the Governors Highway Safety Association
“Office Space”
Two-Point Comparisons in Politics
47%46%
44%44%
Did We Improve?
Run Charts Show More Context
Need to Avoid Bad Conclusions“The average patient satisfaction
increased from 87.2 to 89%”
A Better Dashboard
Limited information you need to make decisions
Not This…
Overwhelming Data
Sept ‘06
?
Can we predict September?
Can We See Trends?
The Good News…
There is a better way
“X” Control Chart(Chart for Individual Values)
“Every system is perfectly designed to get the results it gets.” (Deming)
Goal = 25 minutes
SD = Standard Deviation, a measure of variation
X and MR Chart Combo
Small Business ExampleRevenue as a Stable Process?
X chart
MR chart
Deming’s 7 Concepts of Variation1. All variation is caused – specific reasons.2. There are 4 types of causes:
1. Common causes 2. Special causes 3. Tampering 4. Structural
3. Managers must distinguish amongst these– Each one requires different managerial actions.
Deming’s 7 Concepts of Variation4. For special causes, get timely data5. For common causes, all data are relevant. – In-depth knowledge of the process being improved is
needed – statistics, flow charts, Pareto, stratification analysis, DOE
6. When all variation is common cause, the system is said to be “stable” and “predictable.”
7. SPC limits let a manager predict future performance with some confidence.
The Funnel Experiment
• Lloyd Nelson, 1987– Suspend a funnel on a stand a
few inches off the ground– Drop 50 marbles
x
A “Stable” System
• Does NOT mean:– Zero variability– System meets customer
requirements
• Means only:– Causes of variation are basically constant over time
We Have to Try Harder!!!• 4 different rules for adjusting the funnel
No adjustmentAdjust relativeto last position
Adjust relativeto center
Learn more – online simulator at http://www.symphonytech.com/dfunnel.htm
So we should do nothing?
“Don’t just do something, stand there.” -- Deming
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Responding to Daily Changes
KB
GOAL
Daily Production AveragePraise Team
PT PT
Are we helping? Is this process stable?
KBKick Butt
Creating a Control Chart
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Upper Control Limit
Lower Control Limit
Step 1: Initial Data• Generally need 20 data
points to calculate control limits
Step 2: Mean & MRs• Calculate mean of the
first 20 points• Calculate the moving
range of the first 20 points– Ex: =ABS(E5-E4)
Step 3: Draw Initial Chart(with Mean line)
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Step 4: Add Control Limits• Calculate “MR-bar”– Average of the 1st 19
MRs
• Calculate Control Limits– LCL = Mean – 3*(MR bar)/1.126– UCL = Mean + 3*(MR bar)/1.126
Step 5: Review Chart
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Special Cause?
Step 6: Revise Limits
Step 7: Evaluate Over Time
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Step 7: Evaluate Over Time
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Step 7: Shift the Limits
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“Western Electric” Rules (1956)• 8 consecutive points on same side of mean
• 6 consecutive points moving same direction
• 14 alternating up/down points in a row
• Any single point above or below 3-sigma LCL or UCL
– Full rules http://bit.ly/WErules
Process Shifts
• If you made a change that you expected to improve the system, use a control chart to test the hypothesis
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Process Shift
Daily TAT
Long-Term Process Shifts
NOT Understanding Variation Leads To…
• Pressuring people to get better results by working harder within the same system
• Wasting time looking for explanations of a perceived trend when nothing has changed
• Taking other actions when it would have been better to do nothing
• Not focusing on systemic improvements
Isn’t it always the system?
It’s (almost) always the system.
Q&A / Contact Info• Email:
– [email protected] • Blog:
– www.leanblog.org• Twitter:
– @MarkGraban• Books:
– www.LeanHospitalsBook.com– www.HCkaizen.com