These slides are part of the ESTIEM Lean Six Sigma Green Belt course which also includes 13hr of video by Gregory H. Watson. For more info about the ESTIEM Lean Six Sigma Green Belt course visit https://internal.estiem.org/leansixsigma

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Exploratory Data Analysis (EDA)
for publication
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What do you remember about DMAIC?
Project
Charter
SIPOC
EDA
VA vs.
NVA
DEFINE

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Agenda
▪ What is Minitab?
▪ What is EDA?
▪ 4 tools used in EDA
▪ Practice of interpreting the charts
▪ Making an analysis with Minitab

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What is Minitab?
Minitab is a lot like Excel…
▪ Statistical program for data
analysis
▪ Holds data in cells
… but also rather different!
▪ Not possible to use formulas in cells.
The cells in Minitab merely hold
values.
▪ Additional tools for statistical analysis
compared to excel e.g.
▪ I-chart
▪ ANOVA
▪ Control chart
▪ Capability analyses
● Certain things are easier to do in Excel and other things in Minitab
● Used together, they are powerful!

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How to import data into Minitab
▪ As a rule of thumb, the data should be prepared in Excel
▪ Do all cell-based calculations in Excel
▪ Organize the data so that one column holds data related to one variable
▪ The first row of the data column should be the label/title of the column
▪ Simply copy - paste the data from Excel cells to Minitab cells
▪ The import data - function can also be used but copying is easier!

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How to do simple analyses with Minitab?
Most of the statistical tools can
be found under Stat and Graph

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What is EDA?

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What is Exploratory Data Analysis?
“The purpose of Exploratory Data Analysis (is) to rapidly investigate the
performance of a process and determine quickly where the
improvement effort should be focused for further action.”

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What is Exploratory Data Analysis?
Exploring the current
data about the process
by making many charts
Where should the drill
down focus on?
“The purpose of Exploratory Data Analysis (is) to rapidly investigate the
performance of a process and determine quickly where the
improvement effort should be focused for further action.”

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EDA can be used in different phases of
DMAIC
Define
Focuses direction
Get first insights
of the data
Measure
Identify & quantify
rational subgroups
Analyze
Support Prioritization

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Different types of Data Analysis
Exploratory
▪ Finding the right questions
▪ What can I try easily?
▪ How do I study what’s going
on in here?
▪ “An attitude AND a flexibility
AND some graphs” - Tukey
Confirmatory
▪ Answering well formulated
questions
▪ Confirming hypotheses
▪ Conducting well planned
experiments
▪ Statistical hypothesis testing
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Today we talk about…

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CATAPULT INC

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First, let’s remember some basic definitions
• Average = Mean = Sum / N
• Median = The middle value
• Mode = The most common value
0
5
10
15
20
25
1 2 3 4 5
Grades
Mean = 3,29
Median = 3 Mode = 4

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I-chart
Pareto
Process
Capability
Analysis
Boxplot

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The four tools each have their own strengths
in understanding the process performance
I-chart
Capability
Analysis
Pareto chart
Boxplot
Show a time sequence – were there time based
differences?
Performance of the process against customer
requirement or target for the process
Prioritize e.g. the defects/focus areas
Differences between the rational subgroups

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The four tools each have their own strengths
in understanding the process performance
I-chart
Capability
Analysis
Pareto chart
Boxplot
The Best of the Best and
The Worst of the Worst
Flaw of averages
I chart with stages

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I-chart – How to read?
Mean Control
Limits
Special
Cause of
Variation
Time /
observation
number
Control
Limits

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I-chart – How are control limits calculated?
Control
Limits
Control
Limits
+/- 3 std

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Let’s now, try to understand why
the daily output differs in a
production line

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0
20
40
60
80
100
120
Daily output per Machine
(average)
1 2 3 4 5 6 107 8 9 1112
The daily outputs per machine for a different
process, where would you focus your inquiry?

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0
20
40
60
80
100
120
Daily output per Machine
(average)
1 2 3 4 5 6 107 8 9 1112
Looking at the variation reveals new aspects,
where would you focus now?

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I-Chart with stages – How to read?
(Can be four different I-Charts)

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BOB’s and WOW’s?
Where would you focus your inquiry?

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We rely on averages, which hide the true
improvement levers

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The four tools each have their own strengths
in understanding the process performance
I-chart
Capability
Analysis
Pareto chart
Boxplot
Settings of a machines
”Nuts and bolts”
Difference between machines
”Nuts and bolts”
Difference betweet control and
specification limits

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Remember the bolts…
Bolt needs to be exact size in order to fit the nut
• Above 605 → doesn’t fit in
• Below 595 → doesn’t hold tight

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Which settings is the best for the machine?

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Which machine is the best one?
Some numbers would help on interpreting the differences, right?

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So, which setting is better?
Cp Cpk
0.5 0.25
Cp Cpk
0.5 0.49

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How is process capability calculated?
Variation of process respect to
specification limits
Variation of process respect to
the closest specification limit

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How is process capability calculated?
Cp Cpk
1.14 0.78

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What is the difference between
a control limit and a specification limit?

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Now another of the bolt production lines
with the following specs:
The size must be between 650-680

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What do you think about this process?
Capability analysis of bolt processLSL
650
USL
680
Mean
658,4
N
500
StDev
11.6
Cp
0,43
Cpk
0,24

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Let’s think next of the call center of Catapult
Inc
Your task is to assess the process
The goal is 200 calls per day per person
Discuss, how the process is doing?

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How is the person in our call center doing?
LSL
205
USL
-
Mean
213.7
N
193
StDev
34
Cp
Not calculated
USL is not set
Cpk
0.1

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The four tools each have their own strengths
in understanding the process performance
I-chart
Capability
Analysis
Pareto chart
Boxplot
Production process A
Prioritizing defects
Support function A
Prioritizing improvement opportunities

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What is the Pareto principle?

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80%
of issues
are caused by
20%
of factors

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First, a production center has
identified the reasons for customer
claims in one of the products
Let’s interpret the pareto chart

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67% of defects are caused by two defects
Cumulative count
Possible defects

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Next up: How the pareto chart can be
used to focus the project to most
important areas?

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Which customer groups are the biggest?
To which ones would you focus your inquiry?

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The four tools each have their own strengths
in understanding the process performance
I-chart
Capability
Analysis
Pareto chart
Boxplot
Reading a boxplot
Different process steps
Subgroups

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What is a rational subgroup?

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Some logical group, which might have an effect on
the conditions of the process

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Items in a rational subgroup
are similar within the group
but differ between the groups
E.g. materials from Supplier A form a rational
subgroup, which might have different attributes as
the same materials produced by Supplier B.

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Before we create a boxplot, let’s use this thinking
model on how to approach the data analysis tasks
Identify the
rational
subgroups
Choose the most
important
subgroups
Observe if
differences exist

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Boxplot - how to read?
25% of data here
25% of data here
50% of data here
x
x
Outliers*
Outliers*
Median
* 1,5 times the size of the box above or
below the box

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Different view to data with boxplot
25% of data
25% of data
50% of data
Median =
Mean =
Data set 1
Data set 1
Can be added to the
graph in Minitab
from options

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First, a production process where you are
interested in comparing the output of 4
workers in the process
What is different between the workers?

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Boxplots can describe the difference
between workers in the process

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The four tools each have their own strengths
in understanding the process performance
I-chart
Capability
Analysis
Pareto chart
Boxplot
Show a time sequence – were there time based
differences?
Performance of the process against customer
requirement or target for the process
Prioritize e.g. the defects/focus areas
Differences between the rational subgroups

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I-chart
Pareto
Process
Capability
Analysis
Boxplot

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Time for a thinking exercise!
We’re investigating an invoicing process with 6
persons.
The process daily output should be 1200 per
day (200/person).

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First task, you would like to
understand how well the target of
1200 daily invoices is reached.
Which graph would you use?

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Next, you’re interested in seeing how the
invoicing has changed over time
Which graph would you use?

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Third thing, you would like to understand
the differences between the 6 persons
doing invoicing
Which graph would you use?

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Lastly, you would like to know which
invoices are the most common, i.e. where
you should focus your inquiry
Which graph would you use?

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Time to work…

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SPONSOR MESSAGE
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It’s Feedback time!
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Persons giving feedback
Link to the feedback form
(can be found on Schoology and
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Instructor to give feedback toPersons giving feedback
INSTRUCTOR 1
INSTRUCTOR 2

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It’s Feedback time!
Feedback box

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Usage license of the
materials
https://creativecommons.org/licenses/by-nc/4.0/legalcode
Contact leansixsigma@estiem.org
for commercial usage of the materials
Materials of the trainings have been created based on the materials provided by
ESTIEM Summer Academy Professor Gregory H. Watson