Download - qc tools for engineers
1 7QC Tools
7QC TOOLS
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3 7QC Tools
But …..Oh, my
God! How do I do
it fast and easily
???
I’m growing fat. I
need to monitor my
body weight for the
next 6 months.
I want to include
exercise in my
daily activities
and follow it up
I want to know the
fat content of each
food item
4 7QC Tools
Don’t worry Tom.,
I am here to help
you.
I will you teach you
some of the QC
tools…
5 7QC Tools
QC tools…What is
that ? That is Quality
control tool. ( In
your case it can be
Quantity Control
tools)
6 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
7 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Check Sheet
8 7QC Tools
Module Objectives
This module will help you to understand
• Concept of Check Sheet
• Reason for using Check Sheet
• Types of Check Sheet
• Steps for creating a Check Sheet
- Check Sheet
9 7QC Tools
Check sheet
The Check Sheet is a data-gathering and
interpretation tool
- Check Sheet
Month ,day
Component
1
2
3
4
5
6
7
8
9
10
4/1 2 3 4Month ,day
Component
1
2
3
4
5
6
7
8
9
10
4/1 2 3 4Month ,day
Component
1
2
3
4
5
6
7
8
9
10
4/1 2 3 4
10 7QC Tools
Reasons for using Check sheets
Check Sheet
Simplifies data collection
distinguishing
between
facts and opinions
To save time
To Have a clarity of
thoughts and data
To gain a better
understanding
Easy to
interpret
- Check Sheet
11 7QC Tools
Measured Data
Check Sheet
Indiscrete value such as height, weight, length, time & temp., Etc.
Types of Check Sheet
- Check Sheet
12 7QC Tools
Measured Data
Check Sheet
Indiscrete value such as height, weight, length, time & temp., Etc.
Counted Data
Discrete value such as no. Of recording errors, no. of Item sold
& Rejections etc.
Types of Check Sheet
- Check Sheet
13 7QC Tools
Measured Data
Check Sheet
Indiscrete value such as height, weight, length, time & temp., Etc.
Counted Data
Discrete value such as no. Of recording errors, no. of Item sold
& Rejections etc.
Primary Data
YES / NO or / X - Type
Types of Check Sheet
- Check Sheet
14 7QC Tools
Measured Data
Check Sheet
Indiscrete value such as height, weight, length, time & temp., Etc.
Counted Data
Discrete value such as no. Of recording errors, no. of Item sold
& Rejections etc.
Primary Data
YES / NO or / X - Type
Ordered Data
1st, 2nd Order …Very Good, Good, No Good … - Type
Types of Check Sheet
- Check Sheet
15 7QC Tools
Measured Data
Check Sheet
Indiscrete value such as height, weight, length, time & temp., Etc.
Counted Data
Discrete value such as no. Of recording errors, no. of Item sold
& Rejections etc.
Primary Data
YES / NO or / X - Type
Ordered Data
1st, 2nd Order …Very Good, Good, No Good … - Type
Point Scale Data
1 Point, 2 Point … etc.
Types of Check Sheet
- Check Sheet
16 7QC Tools
Check Sheet
Measured Data
Counted Data
Primary Data
Point Scale Data
Ordered Data
Indiscrete value such as height, weight, length, time & temp., Etc.
Discrete value such as no. Of recording errors, no. of Item sold
& Rejections etc.
YES / NO or / X - Type
1st, 2nd Order …Very Good, Good, No Good … - Type
1 Point, 2 Point … etc.
Types of Check Sheet
- Check Sheet
17 7QC Tools
Problem solving stages for using Check Sheet
1 Problem
2 Observation
3 Analysis
4 Action
5 Check
6 Standardisation
7 Conclusion
Step no QC story step Can use Cannot use
Check sheets can be used in all stages of Problem solving
- Check Sheet
18 7QC Tools
Steps to create a check sheet
Clarify the measurement objective
Create a form for collecting data
Collect the data
Tally the data
- Check Sheet
19 7QC Tools
Price
Mileage
Power
Style
Suspension
I want to
buy a bike
Clarify the measurement objective
- Check Sheet
20 7QC Tools
Yamaha Crux R TVS Centra Bajaj Caliber HH Passion +
Price
Mileage
Power
Style
Suspension
Total
Measure
Model
Create a form for collecting data
- Check Sheet
21 7QC Tools
Power
Yamaha Crux R 7.6/7500
TVS Centra 7.5/7500
Bajaj Caliber 9.5/8000
HH Passion + 7.5/8000
ModelPower
(bhp/RPM)
Yamaha Crux R 39120
TVS Centra 40470
Bajaj Caliber 42567
HH Passion + 43876
Model Price (Rs.,)
Price
Yamaha Crux R 60
TVS Centra 100
Bajaj Caliber 90
HH Passion + 75
ModelMileage
(Kmpl)
Mileag
e
Style
Yamaha Crux R Yes
TVS Centra Yes
Bajaj Caliber No
HH Passion + Yes
Model
Availability of
adjustable
suspension
Suspension
Yamaha Crux R
TVS Centra
Bajaj Caliber
HH Passion +
Model Style
Collect data
- Check Sheet
22 7QC Tools
Power
Yamaha Crux R 7.6/7500
TVS Centra 7.5/7500
Bajaj Caliber 9.5/8000
HH Passion + 7.5/8000
ModelPower
(bhp/RPM)
Yamaha Crux R 39120
TVS Centra 40470
Bajaj Caliber 42567
HH Passion + 43876
Model Price (Rs.,)
Price
Yamaha Crux R 60
TVS Centra 100
Bajaj Caliber 90
HH Passion + 75
ModelMileage
(Kmpl)
Mileage
Style
Yamaha Crux R Yes
TVS Centra Yes
Bajaj Caliber No
Model
Availability of
adjustable
suspension
Suspension
Yamaha Crux R
TVS Centra
Bajaj Caliber
HH Passion +
Model Style
Collect data
- Check Sheet
23 7QC Tools
Best Criteria
Price lower
Mileage higher
Power higher
Style higher
Suspension more
Measure
Model
Measure
1-5 Scale ( 1-worst 5-best)
Collect data
- Check Sheet
24 7QC Tools
Yamaha Crux R TVS Centra Bajaj Caliber HH Passion +
Price
Mileage
Power
Style
Suspension
Total
Measure
Model
Tally the data
Yamaha Crux R TVS Centra Bajaj Caliber HH Passion +
Price
Mileage
Power
Style
Suspension
Total
Measure
Model
16 21 17 15
- Check Sheet
25 7QC Tools
E1 E2 E1 E2 E1 E2 E1 E2
D1
D2
D1
D2
A2
C1 C2 C1 C2
B1
B2
A1
Other Examples of a Check Sheet – Multivariable chart
- Check Sheet
26 7QC Tools
Other Examples of a Check Sheet – Multivariable chart
< 110 cc > 110 cc Scooty Pep < 110 cc > 110 cc Scooty Pep
Sales
Profit
Sales
Profit
Domestic
Export
March April
Motor cycle Scooterettes Motor cycle Scooterettes
- Check Sheet
27 7QC Tools
Exercise:
There are five machines in a manufacturing cell. Among that
two machines are JH Step 4 passed and another 2 are Step
2 passed and one machine is step 1 passed.
Construct a check sheet to identify the factors which is
influencing the high scrap rate.
The cell is getting operated by 3 workmen in all the three
shifts, among them 2 are undergone cell specific training
The scrap cost of the component is high when it has
happened in the last operation and vice versa
- Check Sheet
28 7QC Tools
1 2 3
Cost
rangeTotal
Cost
range
ShiftTotal
Scrap data
OperatorLevel of
machine
Shift Shift Overall
Total
Cost
rangeTotalMachine
Traini
ng
given
Your check sheet can be like this …
- Check Sheet
29 7QC Tools
1 2 3
A Y 2 1 0
B N 2 2 1
C Y 5 7 9
A Y 1 2 1
B N 11 5 10
C Y 3 4 5
A Y 1 1 0
B N 22 58 45
C Y 6 8 12
A Y 2 1 2
B N 7 9 11
C Y 7 9 10
A Y 2 2 3
B N 1 6 8
C Y 8 9 7
Total 245 394 395
Step 4
Step1
Traini
ng
given
459
M5
M1
M2
M3
M4 Step 2
Step 2
1
2
3
44
5
1
2
3
4
5
76
5
10
32
171
92
90
1
2
3
84
85
9
30
87
64
55
10
22
201
ShiftTotal
Scrap data
29
OperatorLevel of
machine
Shift
Step 4
232
230
MachineCost
rangeTotal
Cost
range
Shift Overall
Total
Cost
rangeTotal
Your check sheet can be like this …
Step 1 machine is
making more scrap
Operator without
training is making more
scrap
- Check Sheet
30 7QC Tools
• The Check Sheet is a data-gathering and interpretation tool
• There are five data type Check Sheets
Measured data check sheets
Counted data check sheets
Primary data check sheets
Ordered data check sheets
Point scale data check sheets
• There are four steps to construct a check sheet
• Use of Multivariable chart for extensive data collection
Summary
- Check Sheet
31 7QC Tools
Pareto diagram
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Pareto Diagram
Co
un
t
Pe
rce
nt
Department
Count 5 4 9
Percent 33.0 22.5 10.0 7.5 6.0 5.0
66
4.0 3.0 2.5 2.0 4.5
Cum % 33.0 55.5 65.5 73.0
45
79.0 84.0 88.0 91.0 93.5 95.5 100.0
20 15 12 10 8 6
Othe
r
Other
s
Stor
es
Inform
ation & Sys
tems
Person
nel
Prod
uctio
n En
gine
ering
Service
Fina
nce
Plan
t Mainten
ance
Marke
ting
Mater
ials
200
150
100
50
0
100
80
60
40
20
0
Pareto Chart of Department
32 7QC Tools
Module objectives
At the end of this session, you will be able to …
Explain Pareto diagram and its usage
Explain steps & construct pareto diagram
Interpret Pareto diagram
- Pareto Diagram
33 7QC Tools
Vilfredo Pareto (1848-1923) , an Italian economist
observed that 20% of the Italian people owned 80%
of their country's accumulated wealth.
Who or What is Pareto?
- Pareto Diagram
34 7QC Tools
Pareto’s Rule
A few causes lead to many defects Vital Few
Pareto's rule states that vital few causes (20% of the
causes) are responsible for a large percentage of the
effect (80% of the effects).
A Pareto diagram is a tool used to identify the vital few
causes and trivial many
- Pareto Diagram
35 7QC Tools
Steps for creating Pareto Diagram
1. Collect data
2. Arrange data in the descending order
3. Calculate the relative % for individual data
4. Calculate the cumulative % for individual data
5. Draw a graph with scales on both axis
6. Draw bar chart based on data
7. Using cumulative % data, draw cumulative curve
8. Identify the VITAL FEW (thumb rule > 70%)
- Pareto Diagram
36 7QC Tools
Step 1 : Data collection from check sheet
Sl.No Department No. of calls registered in the period
week 45 to 50.
1 Production Engineering 10
2 Quality 2
3 Service 12
4 Marketing 45
5 Plant Maintenance 20
6 Factory production 2
7 Manufacturing Planning 1
8 Stores 5
9 Personnel 8
10 Materials 66
11 Finance 15
12 Research & Development 4
13 Information & Systems 6
14 Others 4
Example : Identification of depts. contributing majority of telephone calls
- Pareto Diagram
37 7QC Tools
Step 2 : Arrange data in the descending order
Sl.No Department
1 Materials
2 Marketing
3 Plant Maintenance
4 Finance
5 Service
6 Production Engineering
7 Personnel
8 Information Systems
9 Stores
10 Research & Development
11 Others
12 Quality
13 Factory production
14 Manufacturing Planning
Nos.
66
45
20
15
12
10
8
6
5
4
4
2
2
1
200
- Pareto Diagram
38 7QC Tools
Sl.No Department Nos.
1 Materials 66
2 Marketing 45
3 Plant Maintenance 20
4 Finance 15
5 Service 12
6 Production Engineering 10
7 Personnel 8
8 Information Systems 6
9 Stores 5
10 Research & Development 4
11 Others 4
12 Quality 2
13 Factory production 2
14 Manufacturing Planning 1
200
Relative %
33.0
22.5
10.0
7.5
6.0
5.0
4.0
3.0
2.5
2.0
2.0
1.0
1.0
0.5
100
Step 3 : Calculate the relative % for individual
- Pareto Diagram
39 7QC Tools
Sl.No Department Nos. Relative %
1 Materials 66 33.0
2 Marketing 45 22.5
3 Plant Maintenance 20 10.0
4 Finance 15 7.5
5 Service 12 6.0
6 Production Engineering 10 5.0
7 Personnel 8 4.0
8 Information Systems 6 3.0
9 Stores 5 2.5
10 Research & Development 4 2.0
11 Others 4 2.0
12 Quality 2 1.0
13 Factory production 2 1.0
14 Manufacturing Planning 1 0.5
200 100
Cumulative %
33.0
55.5
65.5
73.0
79.0
84.0
88.0
91.0
93.5
95.5
97.5
98.5
99.5
100.0
Step 4 : Calculate the cumulative % for individual
- Pareto Diagram
40 7QC Tools
0
25
50
75
100
125
150
175
200
Ma
teri
als
Ma
rke
tin
g
Pla
nt
Ma
inte
na
nce
Fin
an
ce
Se
rvic
e
Pro
du
cti
on
En
gin
ee
rin
g
Pe
rso
nn
el
Info
rma
tio
n
Syst
em
s
Sto
res
Re
sea
rch
& D
eve
lop
me
nt
Oth
ers
Qu
ali
ty
Fa
cto
ry p
rod
ucti
on
Ma
nu
factu
rin
g P
lan
nin
g
Dept
In n
os
0
25
50
75
100
Cu
mu
lati
ve
%
Step 5 : Draw a graph with scales on both axis
- Pareto Diagram
41 7QC Tools
66
45
20 15 12 10 8 6 5 4 4 2 2 10
25
50
75
100
125
150
175
200
Ma
teri
als
Ma
rke
tin
g
Pla
nt
Ma
inte
na
nce
Fin
an
ce
Se
rvic
e
Pro
du
cti
on
En
gin
ee
rin
g
Pe
rso
nn
el
Info
rma
tio
n
Syst
em
s
Sto
res
Re
sea
rch
& D
eve
lop
me
nt
Oth
ers
Qu
ali
ty
Fa
cto
ry p
rod
ucti
on
Ma
nu
factu
rin
g P
lan
nin
g
Dept
In n
os
0
25
50
75
100
Cu
mu
lati
ve
%
Step 6 : Draw bar chart based on data
- Pareto Diagram
42 7QC Tools
45
2015 12 10 8 6 5 4 4 2 2 1
66
55.5
65.5
73
79
8488
9193.5
95.597.5 98.5 99.5 100
33
0
25
50
75
100
125
150
175
200
Mate
rials
Mark
eti
ng
Pla
nt
Main
ten
an
ce
Fin
an
ce
Serv
ice
Pro
du
cti
on
En
gin
eeri
ng
Pers
on
nel
Info
rmati
on
Syste
ms
Sto
res
Researc
h &
Develo
pm
en
t
Oth
ers
Qu
ali
ty
Facto
ry
pro
du
cti
on
Man
ufa
ctu
rin
g
Pla
nn
ing
Dept
In n
os
0
25
50
75
100
Cu
mu
lati
ve %
45
2015 12 10 8 6 5 4 4 2 2 1
66
55.5
65.5
73
79
8488
9193.5
95.597.5 98.5 99.5 100
33
0
25
50
75
100
125
150
175
200
Mate
rials
Mark
eti
ng
Pla
nt
Main
ten
an
ce
Fin
an
ce
Serv
ice
Pro
du
cti
on
En
gin
eeri
ng
Pers
on
nel
Info
rmati
on
Syste
ms
Sto
res
Researc
h &
Develo
pm
en
t
Oth
ers
Qu
ali
ty
Facto
ry
pro
du
cti
on
Man
ufa
ctu
rin
g
Pla
nn
ing
Dept
In n
os
0
25
50
75
100
Cu
mu
lati
ve %
Step 7 : Using cumulative % data, draw cumulative curve
- Pareto Diagram
43 7QC Tools
Now let’s construct the Pareto using Minitab…
- Pareto Diagram
44 7QC Tools
Enter Department
details in column C1
Enter phone call details in
column C2
Data entry sheet - Minitab
- Pareto Diagram
45 7QC Tools
Navigation details in MINITAB
Select Stat > Quality tools
> Pareto chart
- Pareto Diagram
46 7QC Tools
Select Chart defects
table
Place cursor in labels in
and select C1
Place cursor in
Frequencies in and select
C2
Data entry to tables in MINITAB
- Pareto Diagram
47 7QC Tools
Click OK
- Pareto Diagram
48 7QC Tools
Co
un
t
Pe
rce
nt
Department
Count 5 4 9
Percent 33.0 22.5 10.0 7.5 6.0 5.0
66
4.0 3.0 2.5 2.0 4.5
Cum % 33.0 55.5 65.5 73.0
45
79.0 84.0 88.0 91.0 93.5 95.5 100.0
20 15 12 10 8 6
Othe
r
Other
s
Stor
es
Inform
ation & Sys
tems
Person
nel
Prod
uctio
n En
gine
ering
Service
Fina
nce
Plan
t Mainten
ance
Marke
ting
Mater
ials
200
150
100
50
0
100
80
60
40
20
0
Pareto Chart of Department
Graphical display in MINITAB
- Pareto Diagram
49 7QC Tools
Co
un
t
Pe
rce
nt
Department
Count 5 4 9
Percent 33.0 22.5 10.0 7.5 6.0 5.0
66
4.0 3.0 2.5 2.0 4.5
Cum % 33.0 55.5 65.5 73.0
45
79.0 84.0 88.0 91.0 93.5 95.5 100.0
20 15 12 10 8 6
Othe
r
Other
s
Stor
es
Inform
ation & Sys
tems
Person
nel
Prod
uctio
n En
gine
ering
Service
Fina
nce
Plan
t Mainten
ance
Marke
ting
Mater
ials
200
150
100
50
0
100
80
60
40
20
0
Pareto Chart of Department
How do we interpret a Pareto Chart?
Draw horizontal line at cumulative 70% for effect
70 %
Draw vertical line from the intersection for vital few causes
Vital Few
- Pareto Diagram
50 7QC Tools
Exercises…
1. Tool setting time in Crankshaft cell
3. Breakdown hours of furnaces
2. Internal customer complaints of Engine assly.
Operation Sec
Keyway milling 2.4
Profile Grinding 1.5
Crankpin Hole Drilling 0.6
Fine Boring 0.6
Boss Grinding 0.6
Thread Rolling 0.2
Induction Hardening 0
CGCF 40
SQF 5.5
PHF 2.5
TF 1.5
Crank case 277
Cylinder complete 61
Cylinder head 45
Cover clutch 40
Let’s use
- Pareto Diagram
51 7QC Tools
Results…
What is your result?
2. Internal customer complaints of Engine assly. 1. Tool setting time in Crankshaft cell
3. Breakdown hours of furnaces
- Pareto Diagram
52 7QC Tools
Summary
A few causes lead to many defects Pareto's 20:80 rule:
Co
un
t
Pe
rce
nt
Department
Count 5 4 9
Percent 33.0 22.5 10.0 7.5 6.0 5.0
66
4.0 3.0 2.5 2.0 4.5
Cum % 33.0 55.5 65.5 73.0
45
79.0 84.0 88.0 91.0 93.5 95.5 100.0
20 15 12 10 8 6
Othe
r
Other
s
Stor
es
Inform
ation & Sys
tems
Person
nel
Prod
uctio
n En
gine
ering
Service
Fina
nce
Plan
t Mainten
ance
Marke
ting
Mater
ials
200
150
100
50
0
100
80
60
40
20
0
Pareto Chart of Department
A Pareto diagram is a tool used to identify the vital few causes
Vital Few
- Pareto Diagram
53 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Cause & Effect Diagram
54 7QC Tools
At the end of this module, you will be able to :
Explain the usage of Cause and Effect diagram
Construct a Cause and Effect diagram
Module objectives
- Cause & Effect Diagram
55 7QC Tools
What is a Cause and Effect diagram?
Example – Analysis of Poor Vehicle Mileage
A graphical tool that helps to identify, sort and display possible
causes of a problem or quality characteristics.
It is also called as „Ishikawa diagram’ or „Fishbone diagram’.
- Cause & Effect Diagram
56 7QC Tools
Why should we use a Cause and Effect diagram?
Structured approach to determine the root causes of a problem
or quality characteristic
Indicates possible causes of variation in a process
Encourages group participation and utilizes group knowledge
Identifies areas where data should be collected for further study
- Cause & Effect Diagram
57 7QC Tools
Step- by - step procedure
to construct a Cause and Effect diagram
- Cause & Effect Diagram
58 7QC Tools
Step 1 - Identify and clearly define the outcome or EFFECT
to be analyzed
Decide on the effect to be examined. Effects are stated as particular quality
characteristics, problems resulting from work, planning objectives such as
• Poor mileage
• Higher scrap
• Delay in product development
• Lower customer conversion rates
Remember, an effect may be positive (an objective) or negative (a problem),
depending upon the issue that‟s being discussed.
e.g. Positive effect – Zero defect, 100% Service level
Negative effect – High engine noise, Low productivity
- Cause & Effect Diagram
59 7QC Tools
Example for construction
Effect:
- Cause & Effect Diagram
Poor Vehicle Mileage
60 7QC Tools
Step 2 – Draw the SPINE and create EFFECT BOX
Poor Vehicle
Mileage
Spine
Effect box
- Cause & Effect Diagram
61 7QC Tools
Step 3 – Identify the main CAUSES contributing to the
effect being studied
Establish the main causes, or categories, under which other possible causes are
listed. Commonly used categories are
• 4Ms - Men, Method, Material, Machinery
• 4Ps – Policies, Procedures, People, Plant
• Environment – significantly important 5th category
Write the main categories above and below the spine
Draw a box around each category label and use a diagonal line to form a
branch connecting the box to the spine.
- Cause & Effect Diagram
62 7QC Tools
Step 3 – Identify the main Causes contributing to the effect
being studied continued…
Poor Vehicle
Mileage
Method Machine
Material Men
- Cause & Effect Diagram
63 7QC Tools
Step 4 – For each major factors, identify other specific
factors which may be the Causes of the Effect
Poor Vehicle
Mileage
Method Machine
Material Men
Under inflated
tyres
Carburettor
adjustments
Use wrong
gears
Drive too
fast
Poor
maintenance
Poor driving
habits
Improper
lubrication
Wrong
Octane fuel
- Cause & Effect Diagram
64 7QC Tools
Step 5 – Identify increasing more detailed levels of causes
Poor Vehicle
Mileage
Method Machine
Material Men
Under inflated
tyres
Carburettor
adjustments
Use wrong
gears
Drive too
fast
Poor
maintenance
Poor driving
habits
Improper
lubrication
Wrong
Octane fuel
Focus
area
- Cause & Effect Diagram
65 7QC Tools
No oil change
Wrong oil
Don‟t know right oil
No Owner‟s Manual
Resource problem
Don‟t know recommended octane
No Owner‟s Manual
Level 1
Level 2
Level 3
Level 4 Material
Poor Vehicle
Mileage
Improper
lubrication
Wrong
Octane fuel
Step 5 – Identify increasing more detailed levels of causes
continued…
- Cause & Effect Diagram
66 7QC Tools
Step 5 – Identify increasing more detailed levels of causes
continued…
Poor Vehicle
Mileage
Method Machine
Material Men
Under-inflated tyres
Carburettor
adjustments
Use wrong
gears
Drive too
fast
Poor
maintenance
Poor driving
habits
Improper
lubrication
Wrong
Octane fuel
No record of tyre pressure
Difficult air-stems
Too rich
Fuel mix Unskilled mechanic Poor design
Can‟t hear engine
Impatience Poor hearing
Always late
No awareness
Money.
Poor trg
“When in Rome…”
No oil change
Wrong oil
Money
Don‟t know right oil
Don‟t know recommended
octane
No Owner‟s Manual
Level 1
Level 2
Level 3
Level 4 All the causes are not captured here due to space constraint on the screen.
No Owner‟s
Manual
Done for all
CAUSES
- Cause & Effect Diagram
67 7QC Tools
Step 6 – Analyse the diagram
Look at the balance of the diagram
• Thick cluster in a area indicates need for further study
• A main category having only a few specific causes may indicate a need for
further identification of causes
Look for the causes that appear repeatedly. These may represent root causes
Look for what you can measure in each cause so you can quantify the effects
of any changes you make
Most importantly, identify and circle the causes that you can take action on
- Cause & Effect Diagram
68 7QC Tools
Men Material
Poor Vehicle
Mileage
Method Machine
Under-inflated tyres
Carburettor
adjustments
Use wrong
gears
Drive too
fast
Poor
maintenance
Poor driving
habits
Improper
lubrication
Wrong
Octane fuel
No record of tyre pressure
Difficult air-stems
Too rich
Fuel mix Unskilled mechanic Poor design
Can‟t hear engine
Impatience Poor hearing
Always late
No awareness
Money.
Poor trg
“When in Rome…”
No oil change
Wrong oil
Money.
Don‟t know right oil
Don‟t know recommended
octane
No Owner‟s Manual
Level 1
Level 2
Level 3
Level 4 All the causes are not captured here due to space constraint on the screen.
Step 6 – Analyse the diagram continued…
No Owner‟s
Manual
- Cause & Effect Diagram
69 7QC Tools
We may like to do cause-verification.
Prioritisation of causes identified in Cause and Effect diagram
Case 1 – Known causes with spec. limits.
Step 6 – Analyse the diagram continued…
- Cause & Effect Diagram
4M Cause Specification Investigation Analysis
Man No focused training Functionwise
trainingGeneric
No method to measure
operator's skills
Skill matrix for
each workmenNo skill matrix
No OJTPractical training
at genbaNo OJT
Workmen not trained in
specific jobs
Need based
training
Common
module given
MaterialModule content is
academic oriented
Content should be
specific need
based
Theory based
Method
70 7QC Tools
Effort
Impact
High
High
Low
Low
High impact
Low effort
Prioritisation of causes identified in Cause and Effect diagram
Case 2 – Subjective causes
We may use Four-blocker method
Step 6 – Analyse the diagram continued…
- Cause & Effect Diagram
1 2
3 4
71 7QC Tools
Step 6 – Analyse the diagram continued…
Prioritisation of causes identified in Cause and Effect diagram
Case 2 – Unknown causes appearing for the 1st time
Such causes need to the explored further
- Cause & Effect Diagram
72 7QC Tools
Summary – Cause and Effect diagram
A graphical tool that helps to identify, sort and display possible
causes of a problem or quality characteristics
Structured approach to determine the root causes of a problem
Can you recall?
- Cause & Effect Diagram
73 7QC Tools
Late arrival
of train
at station
Method Machine
Material Men
Group 3
Group 1 Group 2
Group 4
- Cause & Effect Diagram
Lets do an exercise on Cause & Effect Diagram
74 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Graph & Control Charts
75 7QC Tools
Graphs
- Graph & Control Charts
76 7QC Tools
Module Objectives
This module will help you to understand
• Concept for Graph
• Reasons for using Graphs
• Types of Graphs
• Construction and interpretation of Graphs
- Graph & Control Charts
77 7QC Tools
Graph
Graph is a visual representation tool used for showing the
relationship between two or more variables
- Graph & Control Charts
78 7QC Tools
Facilitate in understanding
the data
Quick and direct Easy to remember
Highlight most
important facts
Graph
- Graph & Control Charts
79 7QC Tools
Types of Graphs
• Line graph
•Bar graph
• Pie chart
- Graph & Control Charts
M1
M2
M3
M4
M5
0
10
20
30
40
50
60
70
80
90
100
M1 M2 M3 M4 M5
Studid
Studname
40
45
42 42 42
43
37
38
39
40
41
42
43
44
45
46
Jan Feb Mar Apr May Jun
80 7QC Tools
Line graph
A line graph is a way to summarize how two or more
pieces of variables are related and how they vary
depending on one another
- Graph & Control Charts
40
45
42 42 42
43
37
38
39
40
41
42
43
44
45
46
Jan Feb Mar Apr May Jun
81 7QC Tools
Construction of line graph
Step no:1 - gathering data
• Data must be chronological or sequential form. (At least 25 or more
samples must be taken in order to get an accurate run chart)
Month Weight in Kg
Mar 55
Apr 57
May 58
Jun 60
Jul 62
Aug 63
Sep 62
Oct 61
Nov 61
- Graph & Control Charts
82 7QC Tools
Construction of line graph
Month Weight in Kg
Mar 55
Apr 57
May 58
Jun 60
Jul 62
Aug 63
Sep 62
Oct 61
Nov 61
Step no:2 – organising the data
• Divide the data into two sets of variable – X and Y ( Dependant
variable as Y and independent variable as X )
X Y
- Graph & Control Charts
83 7QC Tools
Step no:3 – charting the data
• Plot the y values versus the x values using an appropriate scale
that will make the points on the graph visible
• Construct a best fit line that passes through the points
Trend of weight over 9 months
55
5758
60
6263
6261
50
52
54
56
58
60
62
64
66
68
Mar Apr May Jun Jul Aug Sep Oct
Wei
ght
(gra
ms)
Construction of line graph
- Graph & Control Charts
84 7QC Tools
Use of MINITAB to
Construct graphs
- Graph & Control Charts
85 7QC Tools
General layout of MINITAB 14
New worksheet
Worksheet – Data
entry in this region
- Graph & Control Charts
86 7QC Tools
Various types of graphs in MINITAB
- Graph & Control Charts
87 7QC Tools
Minitab - graphs
Scatter plot
Data
- Graph & Control Charts
88 7QC Tools
Minitab - graphs
Types of plot
- Graph & Control Charts
89 7QC Tools
Minitab - graphs
Select X & Y
variable
- Graph & Control Charts
90 7QC Tools
Minitab - graphs
Line graph
Options to modify the
graph to get data label
- Graph & Control Charts
91 7QC Tools
Minitab - graphs
Window to get the
data label in graph
- Graph & Control Charts
92 7QC Tools
Month
We
igh
t in
Kg
NovSepJulMayMar
63
62
61
60
59
58
57
56
55
54
6161
62
63
62
60
58
57
55
Scatterplot of Weight in Kg vs Month
The Final Graph
Line graph of Weight vs Month
- Graph & Control Charts
93 7QC Tools
Bar graph
Bar graphs are the tools to represent the data in
the form of bars to easily identify the trends and
patterns
- Graph & Control Charts
0
10
20
30
40
50
60
70
80
90
100
M1 M2 M3 M4 M5
Studid
Studname
94 7QC Tools
Types of Bar graph
• Clustered Bar graph
• Stacked Bar graph
0
10
20
30
40
50
60
1993 1994 1995 1996 1997 1998 1999 2000
Year
Nu
mb
er o
f p
oli
ce o
ffic
ers
0
10
20
30
40
50
60
1993 1994 1995 1996 1997 1998 1999 2000
Year
Nu
mb
er o
f p
oli
ce o
ffic
ers
Vertical
Horizontal
Vertical
Horizontal
• Simple Bar graph Vertical
Horizontal
0
10
20
30
40
50
60
1993 1994 1995 1996 1997 1998 1999 2000
Year
Nu
mb
er o
f p
oli
ce o
ffic
ers
Simple Bar graph Clustered Bar graph Stacked Bar graph
- Graph & Control Charts
95 7QC Tools
Characteristics of bar graphs
• Figure numbered and titled
• Bars of equal width
• Different shading or texture to represent different data sets
• Non-numerical variable on horizontal x-axis
• Labels and units included on x and y axes
• Even scales on axes
- Graph & Control Charts
96 7QC Tools
To create bar graph in MINITAB
Bar chart
option
- Graph & Control Charts
97 7QC Tools
To create bar graph in MINITAB
Bar chart types
selection
- Graph & Control Charts
98 7QC Tools
To create bar graph in MINITAB
Selection of X & Y
axis variable
- Graph & Control Charts
99 7QC Tools
To create bar graph in MINITAB
Options to modify
the graph to get
data label
- Graph & Control Charts
100 7QC Tools
Year
No
., o
f P
olic
e o
ffic
ers
20001999199819971996199519941993
60
50
40
30
20
10
0
56
5149
4745
48
52
55
Chart of No., of Police officers vs Year
The Final Bar-Chart…..
- Graph & Control Charts
101 7QC Tools
To create clustered-bar graph in Minitab
- Graph & Control Charts
102 7QC Tools
To create clustered-bar graph in Minitab
- Graph & Control Charts
103 7QC Tools
Da
ta
C1
2000
1999
1998
1997
1996
1995
1994
1993
Nor
thW
est
East
No rt
hW
est
East
Nor
thW
est
East
Nor
thW
est
East
Nor
thW
est
East
Nor
thW
est
East
No rt
hW
est
East
Nor
thW
est
East
60
50
40
30
20
10
0
10
32
55
12
33
52
15
35
48
14
42
45
18
52
47
15
45
49
12
42
51
10
32
56
The Final Clustered Bar-Chart…..
- Graph & Control Charts
104 7QC Tools
To create stacked bar graph in Minitab
- Graph & Control Charts
105 7QC Tools
To create clustered-bar graph in Minitab
- Graph & Control Charts
106 7QC Tools
Da
ta
20001999199819971996199519941993
60
50
40
30
20
10
0
33
55
35
52
32
48
30
45
16
30
21
35
40
53
45
56
The Final Stacked Bar-Chart…..
- Graph & Control Charts
107 7QC Tools
Pie Chart
A pie chart is a circle graph divided into pieces, each
displaying the size of some related piece of information.
- Graph & Control Charts
M1
M2
M3
M4
M5
108 7QC Tools
Types of Pie Chart
Plant-1 (0)
0%Plant-2 (3)
37%
Plant-3 (2)
24%
R & D (1)
13%
Sp. Wh (1)
13%
Plant 4
13%
Other
25%
• Simple Pie chart
• Pie of Pie chart
• Exploded Pie chart
• Bar of Pie chart
- Graph & Control Charts
109 7QC Tools
To create pie-chart in Minitab
name
variable
- Graph & Control Charts
110 7QC Tools
To create Pie-chart in Minitab
- Graph & Control Charts
111 7QC Tools
55, 62.5%Kerala
11, 12.5%Andhra
22, 25.0%Tamilnadu
Category
Tamilnadu
Andhra
Kerala
Pie Chart of Quantity vs State
- Graph & Control Charts
112 7QC Tools
• Clearly define the information(s) you want to infer from the data
• Experiment with different types of graphs and select the most appropriate
• Plot the graph
• Infer from the graph
Nature of information needed Type of chart
To analyse the distribution
To compare items
To establish time series and to
determine the time frequency
To analyse relationship
Pie chart
Bar graph, Line graph
Bar graph, Line graph
Line graph
Change, rise, growth, increase, decrease,
decline, fluctuation Range, concentration,
Increase with, decrease with, vary with,
despite, correspond to, relate to
Share of, percent of the, smallest, the
majority of
Example
Ranking, larger than, smaller than, equal to
Guidelines for constructing a graph
- Graph & Control Charts
113 7QC Tools
A good graph should
• Be simple and uncluttered
• Have a title and labels
•Show the data without altering the message of the data
• Show accurately the facts
• Clearly shows any trends or differences in the data
- Graph & Control Charts
114 7QC Tools
Exercise:
Open the file : Exercise graph.mtw
Let us do some exercise in Minitab.
There are 8 columns in the Minitab
Try the data to draw line graphs, Bar chart and Pie
chart
- Graph & Control Charts
115 7QC Tools
Your graph may be like this …
Month
Scra
p c
ost
/ E
ng
ine
NovSepJulMayMarJan
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
Line graph of Scrap cost / Engine vs Month
Name of state
Lit
era
cy
ra
te
%
MadhyapradeshKarnatakaAndhrapradeshKeralaTamilnadu
90
80
70
60
50
40
30
20
10
0
6566
72
83
68
Bar chart of Literacy rate % vs Name of state
8, 8.0%Foreign
8, 8.0%Science fiction
11, 11.0%Horror
14, 14.0%Drama
14, 14.0%Romance
18, 18.0%Action
27, 27.0%Comedy
Category
Horror
Science fiction
Foreign
Comedy
Action
Romance
Drama
Pie Chart of Number of movie vs Type of movie
Da
ta
Month 1 JulJunMayAprMarFebJan
60
50
40
30
20
10
0
Variable
Weight Y
Weight Z
Stacked bar chart of Weight Y, Weight Z vs Month 1
- Graph & Control Charts
116 7QC Tools
• Graph is a visual representation tool used for
showing the relationship between two or more
variables
• Line graph, Bar graph and Pie chart are most
commonly used graphs
Summary
- Graph & Control Charts
117 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Histogram
Histogram
118 7QC Tools
At the end of this module, you will be able to :
Explain the construction of a histogram
Interpret output data from a histogram
Construct a histogram using Minitab software
Module objectives
- Histogram
119 7QC Tools
What do we need to infer from this data?
Battery failure data for 56 Pep vehicles
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
1 60 15 187 29 263 43 174
2 37 16 121 30 352 44 145
3 32 17 297 31 290 45 309
4 163 18 134 32 316 46 152
5 230 19 331 33 283 47 338
6 300 20 261 34 304 48 270
7 265 21 220 35 264 49 424
8 166 22 389 36 319 50 313
9 78 23 129 37 287 51 273
10 196 24 278 38 252 52 321
11 194 25 355 39 143 53 369
12 115 26 286 40 359 54 256
13 182 27 249 41 267 55 293
14 294 28 294 42 156 56 270
- Histogram
120 7QC Tools
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
1 60 15 187 29 263 43 174
2 37 16 121 30 352 44 145
3 32 17 297 31 290 45 309
4 163 18 134 32 316 46 152
5 230 19 331 33 283 47 338
6 300 20 261 34 304 48 270
7 265 21 220 35 264 49 424
8 166 22 389 36 319 50 313
9 78 23 129 37 287 51 273
10 196 24 278 38 252 52 321
11 194 25 355 39 143 53 369
12 115 26 286 40 359 54 256
13 182 27 249 41 267 55 293
14 294 28 294 42 156 56 270
How do you find that?
We can use Histogram.
How the data
looks like
Range of
battery life
Mean of
battery life
- Histogram
121 7QC Tools
Histogram
45
16
18
6
1
0
2
4
6
8
10
12
14
16
18
20
36-45 46-55 56-65 66-75 76-85 96-95
Marks obtained
Fre
qu
en
cy
What is a histogram?
Example – Marks obtained by 50 students in a class
Range of
marks
No. of
students
A histogram is a graphical representation of frequency distribution of
data
Majority have scored in-
between 56-75
- Histogram
122 7QC Tools
To display large amounts of data values in a relatively simple chart form
To tell relative frequency of occurrence
To understand the central tendency & spread of the data
To understand overall distribution of the data
Where to use a histogram?
- Histogram
123 7QC Tools
Step- by - step procedure
to construct a histogram
- Histogram
124 7QC Tools
Example
Battery failure data for 56 Pep vehicles
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
1 60 15 187 29 263 43 174
2 37 16 121 30 352 44 145
3 32 17 297 31 290 45 309
4 163 18 134 32 316 46 152
5 230 19 331 33 283 47 338
6 300 20 261 34 304 48 270
7 265 21 220 35 264 49 424
8 166 22 389 36 319 50 313
9 78 23 129 37 287 51 273
10 196 24 278 38 252 52 321
11 194 25 355 39 143 53 369
12 115 26 286 40 359 54 256
13 182 27 249 41 267 55 293
14 294 28 294 42 156 56 270
- Histogram
125 7QC Tools
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
Vehicle
No.
Battery
life, days
1 60 15 187 29 263 43 174
2 37 16 121 30 352 44 145
3 32 17 297 31 290 45 309
4 163 18 134 32 316 46 152
5 230 19 331 33 283 47 338
6 300 20 261 34 304 48 270
7 265 21 220 35 264 49 424
8 166 22 389 36 319 50 313
9 78 23 129 37 287 51 273
10 196 24 278 38 252 52 321
11 194 25 355 39 143 53 369
12 115 26 286 40 359 54 256
13 182 27 249 41 267 55 293
14 294 28 294 42 156 56 270
Step 1 - Determine the range (R) of the data
Obtain the largest & smallest values from the data
Calculate the R = Largest value – Smallest value
Range = 424 – 32
Range = 392
Smallest
observed value
Largest
observed value
- Histogram
126 7QC Tools
Step 2 - Determine the class interval & interval breadth
of the data
where n is the total no. of observations
Class interval = n
Here, n = 56, therefore,
Class interval =
Class interval = 7.49 = 7, after rounding it off to nearest integer
56
Now , to determine class breadth,
Class breadth = R /
Class breadth = 392 / 7
Class breadth = 56
n
- Histogram
127 7QC Tools
Step 3 – Create table of upper & lower limits of
class-intervals
The lower limit of the first class-interval is the lowest observed value in the data.
i.e. Lower limit of the 1st class = 32
Upper limit = Lower limit + Class breadth
= 32 + 56
= 88
To determine the next class-interval, start from the next number i.e. 89
So, Lower limit of 2nd class = 89
Upper limit = 89 + 56 = 145
Similarly, we can decide the class limits for all 7 class-intervals…
- Histogram
128 7QC Tools
Step 3 – Create table of upper & lower limits of
class-intervals continued…
Class interval Lower limit Upper limit
1 32 88
2 89 145
3 146 202
4 203 259
5 260 314
6 315 371
7 372 428
- Histogram
129 7QC Tools
Step 4 – Prepare frequency distribution table
How many pieces of data fall into each of the class?
# Class Frequency marks Frequency
1
2
3
4
5
6
7
32 – 88
89 – 145
146 – 202
203 – 259
260 – 316
317- 373
374 – 430
IIII
IIII I
IIII IIII
IIII
IIII IIII IIII IIII II
IIII III
II
4
6
9
5
22
8
2
Total 56
- Histogram
130 7QC Tools
Step 5 – Prepare a histogram [a bar graph] of class vs
frequency
Histogram - Battery failures [Pep]
46
9
5
22
8
2
0
5
10
15
20
25
32-88 89-145 146-202 203-259 216-316 317-373 374-430
No. of days of usage
No
. o
f fa
ilu
res
Class
Frequency
Now, what do you interpret from this histogram?
- Histogram
131 7QC Tools
Introduction to few terms
Central
tendency
Spread
Central tendency - A measure of location of the middle or the centre of a distribution
The mean is the most commonly used measure of central tendency
Spread or Dispersion - Describes how much the observations vary around the
central tendency
A histogram
- Histogram
132 7QC Tools
What do you interpret from this histogram?
Histogram - Battery failures [Pep]
46
9
5
22
8
2
0
5
10
15
20
25
32-88 89-145 146-202 203-259 216-316 317-373 374-430
No. of days of usage
No
. o
f fa
ilu
res
Class
Frequency
1. It appears to be a bell-shaped distribution
2. Most of the battery failures seem to occur for the the period of
216 – 316 days of usage.i.e. Central tendency is at 216-316 days
3. The spread appears to be higher
Period with
maximum no. of
failures
Maximum failures
- Histogram
133 7QC Tools
Interpretations from histograms
Histogram may be interpreted by asking 3 questions:
1. Is the process performing within specification limits?
2. Does the process seem to exhibit wide variation?
3. If action needs to be taken on the process, what action is appropriate?
The answer to these 3 questions lies in analyzing 3 characteristics of
the histogram.
- Histogram
134 7QC Tools
Interpretations from histograms continued…
1. Is the process performing within specification limits?
Analyse: How well is the histogram centered?
The centering of the data provides information on the process aim
about some mean or nominal value.
Process Data
Fre
qu
en
cy
13.012.512.011.511.010.5
LSL USL
1
3
1
4
14
3
10
8
5
1
Process Capability of Diameter
LSL
Target
Process
mean
- Histogram
Process Data
Freq
uen
cy
13.012.512.011.511.010.5
LSL USL
1
3
1
4
14
3
10
8
5
1
Process Capability of Diameter
USL
135 7QC Tools
2. Does the process seem to exhibit wide variation?
Analyse: How wide is the histogram?
Looking at histogram width defines the variability of
the process about the aim.
Interpretations from histograms continued…
Process Data
Fre
qu
en
cy
13.012.512.011.511.0
LSL USL
22
7
10
12
10
2
3
2
Process Capability of Shaft dia
- Histogram
Process Data
Freq
uen
cy
13.012.512.011.511.010.5
LSL USL
1
3
1
4
14
3
10
8
5
1
Process Capability of Diameter
136 7QC Tools
3. If action needs to be taken on the process, what action is
appropriate?
Analyse: What is the shape of the histogram?
Interpretations from histograms continued…
Distribution other than normal indicates presence of special cause in the process
C9
Fre
qu
en
cy
14121086420
12
10
8
6
4
2
0
1
00
111
0
22
3
6
5
10
12
6
Histogram of C9
Process Data
Fre
qu
en
cy
13.012.512.011.511.0
22
7
10
12
10
2
3
2
Process Capability of Shaft diaNormal Non-
normal
- Histogram
Process Data
Freq
uen
cy
13.012.512.011.511.010.5
LSL USL
1
3
1
4
14
3
10
8
5
1
Process Capability of Diameter
137 7QC Tools
Depending upon the shape of the histogram
[i.e. distributions ], there are following types of histograms
1. Bell-shaped [normal]
2. Bi-modal [double-peaked]
3. Skewed
Interpretations from histograms continued…
- Histogram
138 7QC Tools
1. Bell-shaped [normal]
Depicted by a bell-shaped curve
• most frequent measurement appears as center of distribution
• less frequent measurements taper gradually at both ends of
distribution
Indicates that a process is running normally (only common causes are
present)
Example: Histogram - Cyld block failures - Victor
1
913
20
29
4238
6357
69
51 5257 59
4541
3833 32
16 14 13 14
40 0 0 0 1
0
10
20
30
40
50
60
70
80
725 4666 8606 12547 16487 20428 24368 28309 32249 36190
Kilometer of usage
No
. o
f fa
ilu
res
Interpretations from histograms continued…
- Histogram
139 7QC Tools
2. Bi-modal [double-peaked]
Distribution appears to have two peaks
May indicate that data from more than one process are mixed together
• Materials may come from two separate vendors
• Samples may have come from two separate machines
Example: Histogram - Fork Gear-shift - Bore finish
1
4
8
5
9
3
0
2
4
6
8
10
0.1 0.17 0.24 0.31 0.38 More
RaF
req
ue
nc
y
Interpretations from histograms continued…
- Histogram
140 7QC Tools
3. Skewed
Appears as an uneven curve; values seem to taper to one side.
Example:
Here most of the values lies in the lower part of the values of histogram
3A. Positively Skewed
Histogram - No. of trucks halted
81
125 4
0
20
40
60
80
100
0-24 25-48 49-72 72-96
Hrs of waiting
No
. o
f tr
ucks
Interpretations from histograms continued…
- Histogram
141 7QC Tools
Histogram - Wheel-rim - Runout
1
6
21 22
0
5
10
15
20
25
0.94 1.02 1.09 More
Runout, mm
Fre
qu
en
cy
Here most of the values lies in the upper part of the values of histogram
3B. Negatively Skewed
Example:
3. Skewed
Appears as an uneven curve; values seem to taper to one side.
Interpretations from histograms continued…
- Histogram
142 7QC Tools
General Rule for Constructing a Histogram
Number of samples
For the histogram to be representative of the true process
behavior, as a general rule, 30 to 50 samples should be
measured.
- Histogram
143 7QC Tools
Construction of a histogram using MINITAB software
- Histogram
144 7QC Tools
Start MINITAB This is the first
screen of MINITAB
Here is the place
for your data
Session
window
- Histogram
145 7QC Tools
Enter the data
in a column,
say, C2
Enter the data
- Histogram
146 7QC Tools
Go to Graph
Histogram
Draw histogram
- Histogram
147 7QC Tools
Select the type
“With Fit…”
Draw histogram continued...
- Histogram
148 7QC Tools
Click Select to
select the
column C2
C2 appears
here
Click OK
Draw histogram continued...
- Histogram
149 7QC Tools
Here is the
histogram
Draw histogram continued...
- Histogram
150 7QC Tools
Histogram
A histogram is a graphical representation of frequency distribution of
data
Histogram is used to understand
• Central tendency
• Spread
• Overall distribution
Different types of histogram are -
• Bell-shaped [normal]
• Bi-modal [double-peaked]
• Skewed
Can you recall?
Summary - Histogram
- Histogram
151 7QC Tools
55 56 61 58 60
66 56 71 48 52
57 56 62 66 61
58 63 67 61 60
55 65 54 55 60
38 54 62 61 61
59 67 57 59 61
61 59 55 62 57
55 59 62 58 60
56 63 64 55 51
Marks
56 45 66
38 35 34
73 37 49
55 69 53
50 32 50
43 50 62
53 67 57
50 50 46
59 67 62
49 45 51
Test scores
47 19 6 40 11
85 17 60 129 69
23 11 41 53 45
47 10 13 86 11
49 44 87 59 28
21 18 88 74 60
44 113 13 44 27
38 45 7 41 152
9 22 37 101 47
252 14 45 90 90
Data
46 48 62 51 47
52 63 56 49 47
48 66 42 54 57
55 48 57 50 53
52 49 58 60 56
47 46 56 51 48
53 47 56 57 49
55 56 49 57 58
49 50 60 56 45
54 54 51 60 52
Data A
Example - 1 Example - 2 Example - 3 Example - 4
Draw Histogram for the following using Minitab application…
- Histogram
152 7QC Tools
Marks
Fre
qu
en
cy
7264564840
20
15
10
5
0
1
2
8
19
16
2
1
0
1
Histogram of Marks
Test scores
Fre
qu
en
cy
7060504030
9
8
7
6
5
4
3
2
1
0
11
33
5
8
4
1
3
1
Histogram of Test scores
Data
Fre
qu
en
cy
240180120600
20
15
10
5
0
1
00
1
2
7
10
19
10
Histogram of Data
Data A
Fre
qu
en
cy
6560555045
10
8
6
4
2
0
1
2
3
7
9
6
10
8
3
1
Histogram of Data A
Solution - 1
Solution - 4
Solution - 2
Solution - 3
Answers
Appears normally
distributed
Appears normally
distributed with
wide variation
Appears + vely
skewed Appears to be a bi-
modal distribution
- Histogram
153 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Scatter Diagram
Temperature
No
of
ice
cre
am
s s
old
35302520151050
110
100
90
80
70
60
50
40
30
20
Scatterplot of No of ice creams sold vs Temperature
154 7QC Tools
Module objectives
At the end of this session, you will be able to …
Explain Scatter diagram and its usage
Explain steps & construct Scatter diagram
Interpret Scatter diagram
- Scatter Diagram
155 7QC Tools
To know kinds of relationships between variables, Scatter
diagram was developed
Sir Francis Galton (1822-1911), by using the theory of linear
regression developed Scatter diagram.
Why Scatter diagram was developed?
- Scatter Diagram
156 7QC Tools
It is a visual display of data which shows the association
between two variables acting continuously on the same item.
What is Scatter diagram?
It illustrates the strength of the correlation between the
variables through the slope of a line.
- Scatter Diagram
157 7QC Tools
Step 1. Collect at least 20-30 paired data points: "paired" data are
measures of both the cause being tested and its supposed effect at one
point in time
Step 2. Draw a graph, with the "cause" on the horizontal axis and the
"effect" on the vertical axis.
Step 3. Determine the lowest and highest value of each variable and mark
the axes accordingly.
Step 4. Plot the paired points on the diagram. If there are multiple pairs
with the same value, draw as many circles around the point as there are
additional pairs with those same values.
Step 5. Identify and classify the pattern of association using the graphs
below of possible shapes and interpretations.
Steps for creating a Scatter Diagram
- Scatter Diagram
158 7QC Tools
Example : No. of ice cream sold against atmospheric temp.
Sno Temperature
Number of Ice-
Creams sold Sno Temperature
Number of
Ice-Creams
sold
1 21 70 17 12 44
2 26 86 18 32 105
3 15 50 19 20 56
4 24 80 20 27 92
5 18 58 21 23 74
6 29 96 22 31 102
7 20 56 23 33 106
8 27 92 24 11 42
9 23 74 25 34 106
10 17 54 26 35 107
11 30 100 27 10 39
12 19 62 28 5 30
13 14 48 29 8 35
14 13 46 30 3 25
15 16 52 31 2 22
16 28 94 32 6 32
Collection of paired data
- Scatter Diagram
159 7QC Tools
Draw the graph
Outside temperature
No o
f ic
e c
ream
s so
ld
In this example,
Temperature (cause) will be indicated by X (horizontal axis) and
Number of Ice-cream sold (Effect) by Y (vertical axis).
- Scatter Diagram
160 7QC Tools
10 20 30 40 50
20
40
60
80
100
120
Outside temperature
No o
f ic
e c
ream
s so
ld
Mark the axes based on lowest and highest values
Highest value in temperature – 35
Highest value in Number of Ice-cream sold - 107
- Scatter Diagram
161 7QC Tools
10 20 30 40 50
20
40
60
80
100
120
Outside temperature
No o
f ic
e c
ream
s so
ld
Plot the data Sno Temperature
Number of Ice-
Creams sold Sno Temperature
Number of
Ice-Creams
sold
1 21 70 17 12 44
2 26 86 18 32 105
3 15 50 19 20 56
4 24 80 20 27 92
5 18 58 21 23 74
6 29 96 22 31 102
7 20 56 23 33 106
8 27 92 24 11 42
9 23 74 25 34 106
10 17 54 26 35 107
11 30 100 27 10 39
12 19 62 28 5 30
13 14 48 29 8 35
14 13 46 30 3 25
15 16 52 31 2 22
16 28 94 32 6 32
- Scatter Diagram
162 7QC Tools
10 20 30 40 50
20
40
60
80
100
120
Outside temperature
No o
f ic
e c
ream
s so
ld
Identify and classify the pattern
- Scatter Diagram
163 7QC Tools
Now let’s construct the Scatter using Minitab…
- Scatter Diagram
164 7QC Tools
Enter Temperature
values in column C1
Enter No of ice creams
sold in column C2
- Scatter Diagram
165 7QC Tools
Select Graph > Scatter plot
- Scatter Diagram
166 7QC Tools
Click OK
Select with
Regression
- Scatter Diagram
167 7QC Tools
Select C1 - X
variables
Select C2 - Y
variables
- Scatter Diagram
168 7QC Tools
Click OK
- Scatter Diagram
169 7QC Tools
Temperature
No
of
ice
cre
am
s s
old
35302520151050
110
100
90
80
70
60
50
40
30
20
Scatterplot of No of ice creams sold vs Temperature
- Scatter Diagram
170 7QC Tools
Temperature
No
of
ice
cre
am
s s
old
35302520151050
110
100
90
80
70
60
50
40
30
20
Scatterplot of No of ice creams sold vs Temperature
How do we interpret this Scatter diagram ?
• Strong relationship between the two variables : If most
of the points fall along an imaginary straight line with either
a positive or negative slope
• No relationship between the two variables : If points are
randomly scattered about the graph
- Scatter Diagram
171 7QC Tools
Temperature
No
of
ice
cre
am
s s
old
35302520151050
110
100
90
80
70
60
50
40
30
20
Scatterplot of No of ice creams sold vs Temperature
Strong
relation
Interpretation
Scatter diagrams show relationships, but do not
prove that one variable causes the other
- Scatter Diagram
172 7QC Tools
0
5
10
15
20
25
30
35
0 5 10 15 20
0
50
100
150
200
250
300
350
0 100 200 300 400
Strong Positive correlation Strong Negative correlation
Types of Scatter Diagram
- Scatter Diagram
173 7QC Tools
Weak Positive correlation Weak Negative correlation
0
10
20
30
40
0 5 10 15 20
0
100
200
300
400
500
0 100 200 300 400
Types of Scatter Diagram
- Scatter Diagram
174 7QC Tools
0
100
200
300
400
500
600
700
0 100 200 300 400
No correlation
Types of Scatter Diagram
- Scatter Diagram
175 7QC Tools
J-shaped /Non linear association
Suggests complex relationships
Types of Scatter Diagram
- Scatter Diagram
176 7QC Tools
No of
Vehicles
Consumable
cost/vehicle
62598 23.9
50614 33.1
35148 45.0
44932 30.6
43669 14.0
26419 42.9
18712 36.8
24466 65.7
30520 55.0
30166 59.2
36100 47.8
39766 40.1
No. of
Engines/m
onth
Power
consumption
/Engine
75349 2.67
81281 2.75
82298 2.66
90763 2.25
93386 2.3
96376 1.7
90361 2
92467 1.8
1. Consumable
cost Vs No. of
Vehicles
2. Compressor
power consump.
Vs No. of Eng.
3. Pressing load Vs interference between hole &
shaft
0.11 2779
0.101 2229
0.106 2421
0.11 2446
0.11 2480
0.107 2563
0.101 2177
0.103 2325
0.099 2185
0.104 2305
PRESSING LOAD
(Kg)
INTERFEREN
CE
Let’s use
Exercises…
- Scatter Diagram
177 7QC Tools
Results…
1. Consumable cost Vs No.
of Vehicles
2. Compressor power
consumption Vs No. of Eng.
Weak negative
correlation
Weak negative
correlation
What is your result?
3. Pressing load Vs interference between hole &
shaft
Strong positive
correlation
- Scatter Diagram
178 7QC Tools
Summary
It is a visual display of two variables acting continuously on the same item.
Scatter diagram
0
20
40
60
80
100
120
0 10 20 30 40
Outside TemperatureN
um
be
r o
f ic
e-c
rea
m
so
ld
It illustrates the strength of the correlation between the variables
0
5
10
15
20
25
30
35
0 5 10 15 20
Strong positive
0
50
100
150
200
250
300
350
0 100 200 300 400
Strong Negative
0
10
20
30
40
0 5 10 15 20
Weak positive
0
100
200
300
400
500
0 100 200 300 400
Weak Negative
0
100
200
300
400
500
600
700
0 100 200 300 400
No relation
It show relationships, but do not prove that one variable causes the other
- Scatter Diagram
179 7QC Tools
Check Sheet
Pareto Diagram
Cause & Effect diagram
Stratification
Scatter Diagram
Graphs
Histogram
7 QC Tools
- Stratification
180 7QC Tools
Stratification is the act of fine tuning the data in order to
make sure of the significance of the assured factors, to the
grass root level.
Stratification
- Stratification
181 7QC Tools
Rep.acct. – Operator not reporting back to duty
for more than 48hrs
Non-reportable acct. – Operator disablement extending
beyond the day of shift but less than
48 hrs
Hosur Mysore
2000-04 2001-04
Reportable accident 47 17
Non reportable accident 179 92
Mandays lost 1476 510
Accident data
Description
- Stratification
182 7QC Tools
Plant No., of accidents Unit Category
Others
42
108
42
108
44
Plant 1
Plant 2
Plant 3
Plant 4
R&D - 16,Sp.WH - 8,Canteen -
10,Civil - 5,SC.Y - 1E.WH-
2,PED - 1,TQC - 1,
Reg - 16,Contractor -
12,Temp.workman - 14,
Supplier- 0, Visitor -0
Reg - 43,Contractor -
22,Temp.workman - 41,
Supplier- 1, Visitor -1
Reg - 16,Contractor -
12,Temp.workman - 14,
Supplier- 0, Visitor -0
Reg - 49,Contractor -
16,Temp.workman - 43,
Supplier- 0, Visitor -0
Reg - 20,Contractor - 11,
Temp.workman - 13,
Supplier- 0, Visitor -0
Fab-15,Engine - 9,Painting -
11,Vehicle - 3,Stores - 4
Fab-25,Engine - 24,Painting -
16,Vehicle - 9,Stores - 20
,Plating - 14
M/C shop - 9,G/Shop -
17,HT/Plating - 8, Stores - 8
Fab-15,Engine - 30,Painting -
19,Vehicle - 15,Stores - 18
,Plating - 11
Accident data sheet
- Stratification
183 7QC Tools
Plant No. of accidents
Plant 1 42
Plant 2 108
Plant 3 42
Plant 4 108
Spares
Warehouse8
R&D 16
Canteen 10
Civil 5
Export
Warehouse2
Others 3
Accident data sheet
- Stratification
184 7QC Tools
According to plant
Plant wise
No
of
accid
en
ts
Othe
rs
Expo
rt war
e ho
use
Cantee
nCivi l
Spar
e war
e ho
use
R &
D
Plan
t 4
Plan
t 3
Plan
t 2
Plan
t 1
120
100
80
60
40
20
032
105
8
16
108
42
108
42
Chart of No of accidents vs Plant wiseN
o o
f accid
en
ts
Plant
- Stratification
185 7QC Tools
Similarly stratification can be done
Unit wise
Workmen category wise
Shift wise
Phenomena wise
Machine/equipment wise
and so on…
186 7QC Tools
Other Stratification methodologies
- Stratification
187 7QC Tools
• Stratification is the act of fine tuning the data in order to
make sure of the significance of the assured factors, to
the grass root level
• Stratification helps to get more information from different
perspective from the same data
Summary
- Stratification