7qc Tools Test
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7QC Tools
7 QC TOOLS Q7T/PPT- 1
7QC Tools
Types
Types of 7QC tools Check CheckSheet Sheet Pareto ParetoDiagram Diagram Cause Cause&&Effect Effectdiagram diagram
77 QC QC Tools Tools
Graph Graph&Control &Controlcharts charts Histogram Histogram Scatter ScatterDiagram Diagram Stratification Stratification
Q7T/PPT- 2
7QC Tools
Check sheet
Check sheet
Q7T/PPT- 3
7QC Tools
What is a check sheet? Why is a check sheet necessary?
Q7T/PPT- 4
Check sheet
7QC Tools
Check sheet
Check sheet Check sheets are forms used for • standardizing • checking results of work • verifying and collecting data
Q7T/PPT- 5
7QC Tools
Check sheet
Types of Check Sheet Discretevalue valuesuch suchas asno. no.Of Of Discrete recordingerrors, errors,no. no.ofofItem Itemsold sold recording Rejectionsetc. etc. &&Rejections
Indiscretevalue valuesuch suchas asheight, height, Indiscrete weight,length, length,time time&&temp., temp.,Etc. Etc. weight,
Measured Measured Data Data PointScale Scale Point Data Data
Point,22Point Point… … 11Point, etc. etc.
Counted Counted Data Data
Check Sheet Ordered Ordered Data Data st nd Order … 11st, ,22nd Order … VeryGood, Good,Good, Good, No NoGood Good Very …- -Type Type …
Q7T/PPT- 6
Primary Primary Data Data YES/ /NO NO or or YES Type √√ / /XX - -Type
7QC Tools
Check sheet
Example of check sheet Defect check sheet Month ,day Component
4/1
2
1 2 3 4 5 6 7 8 9 10
No. of defects Q7T/PPT- 7
3
4
7QC Tools
How to prepare check sheets? • Clarifying the objective • Determining the type of check sheet to use • Deciding which items to check • Creating the check sheet • Recording the data • Tallying the data • Examining the check sheet Q7T/PPT- 8
7QC Tools
Check sheet
Check points for check sheets preparation Below items can be added , as necessary 1. The purpose of the checks 2. The items being checked 3. The methods of the checks 4. The dates and times of the checks 5. The person to perform the checks 6. The results Q7T/PPT- 9
7QC Tools
Pareto
Pareto diagram
Q7T/PPT- 10
7QC Tools
Pareto
Do you remember this? (14th March 2001 - Eden gardens )
Q7T/PPT- 11
7QC Tools
Pareto
Do you remember this? (14th March 2001 - Eden gardens )
Q7T/PPT- 12
7QC Tools
Pareto
Now let’s look at the second innings score board: India SS Das
hit wicket b Gillespie
39
S Ramesh
c ME Waugh b Warne
30
VVS Laxman
c Ponting b McGrath
281
SR Tendulkar
c Gilchrist b Gillespie
10
SC Ganguly
c Gilchrist b McGrath
48
R Dravid
run out
180
N R Mongia
b McGrath
4
Zaheer Khan
not out
23
Harbhajan Singh
not out
8
Total Q7T/PPT- 13
657
7QC Tools
When we observe which batsmen got the maximum runs we can see that Laxman & Dravid got 461 out of the 657 runs. That is about 70% of the runs. 22% of the 9 batsmen who batted got 70% of the runs!
Let’s now observe the Australian 2nd innings score card
Q7T/PPT- 14
Pareto
7QC Tools
Australia M Hayden M Slater J Langer M Waugh S Waugh R Ponting A Gilchrist J Gillespie S Warne M Kasprowicz G McGrath
Q7T/PPT- 15
Pareto
lbw b Tendulkar c Ganguly b Harbhajan c Ramesh b Harbhajan lbw b Raju c Sub B Harbhajan c Das b Harbhajan lbw b Tendulkar c Das b Harbhajan lbw b Tendulkar not out lbw b Harbhajan Total
67 43 28 0 24 0 0 6 0 13 12 212
7QC Tools
Pareto
Who got the wickets?
O
M
R
W
Zaheer Khan
8
4
30
0
V Prasad
3
1
7
0
Harbhajan Singh
30.3
8
73
6
V Raju
15
3
58
1
S Tendulkar
11
3
31
3
S Ganguly
1
0
2
0
Q7T/PPT- 16
7QC Tools
Pareto
When we observe which bowlers got the maximum wickets we can see that Harbhajan & Tendulkar got 9 out of the 11 wickets. That is about 80% of the wickets. 30% of the 6 bowlers who bowled got 80% of the wickets!
This illustrates the Pareto principle
Q7T/PPT- 17
7QC Tools
Pareto
Pareto • Vilfredo Pareto was an Italian engineer in the 19th Century who studied the number of people in various income classes & declared ‘’20% of the people own 80% of the country’s wealth; 80% of the people own 20% of the country’s wealth”
Q7T/PPT- 18
7QC Tools
Pareto
Pareto Principle Pareto principle holds good to the present day in various applications ‘ A few causes lead to many defects; many causes lead to few defects.’ The few causes that lead to many defects are the vital few. The many causes that lead to few defects are the trivial many.
Q7T/PPT- 19
7QC Tools
Pareto
“Get to the biggest problems first” ‘Solve the vital few’
Q7T/PPT- 20
7QC Tools
REMEMBER … The most frequent or most costly events are not always the most important.
e.g. Two fatal accidents deserve more attention than 100 cut fingers.
Q7T/PPT- 21
7QC Tools
Pareto 175
100 100
99.5
98.5
97.5
95.5
93.5
91
88
84 79
150
75
73
55.5 100 75
50 66
33 45
50
25 20
25
15
12
10
8
6
5
4
4
2
2
1
0
Steps
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%)
Q7T/PPT- 22
Quality
Factory production
Manufacturing Planning
Stores
Others
Information Systems
Dept
Research & Development
Service
Personnel
Finance
Production Engineering
Plant Maintenance
Materials
Marketing
0
In %
65.5
125 In nos
Creating a Pareto Diagram
200
7QC Tools
Pareto 200
Sl.No
Q7T/PPT- 23
Department
55.5 100
50 66
33 45
50
25 20
25
15
12
10
8
6
5
4
4
2
2
1
0
No. Of cells regd.
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
Quality
Factory production
Manufacturing Planning
Stores
Others
Information Systems
Dept
Research & Development
Service
Personnel
Finance
Production Engineering
Plant Maintenance
Materials
0
In %
In nos
75
73 65.5
125
75
Period : Week No. 45 To 50 No. Of External Phone Calls
100 100
99.5
98.5
97.5
95.5
93.5
91
88
84 79
150
Marketing
STEP 1
Data collection through check sheet
175
7QC Tools
Pareto 200 175
Department
75
33 45
25 20
15
12
10
8
6
5
4
4
2
2
1
No. Of cells reqd.
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
Quality
Factory production
Manufacturing Planning
Stores
Others
Information Systems
Dept
Research & Development
Service
Personnel
Finance
Production Engineering
Plant Maintenance
Materials
0
In %
50 66
50
0
200 Q7T/PPT- 24
55.5 100
25
No. Of External Phone Calls Sl.No
In nos
Arrange data in the descending order
75
73 65.5
125
Marketing
STEP 2
100 100
99.5
98.5
97.5
95.5
93.5
91
88
84 79
150
7QC Tools
Pareto 200 175
In nos
75
Department
45
25 20
15
12
10
8
6
5
4
4
2
2
1
0
Relative %
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
Quality
Factory production
Manufacturing Planning
Stores
Others
Information Systems
Dept
Research & Development
Service
Personnel
Finance
Production Engineering
Plant Maintenance
Materials
0
Nos.
200
33
25
1
Q7T/PPT- 25
50 66
50
No. Of External Phone Calls Sl.No
55.5 100
In %
Calculate the relative % for individual
75
73 65.5
125
Marketing
STEP 3
100 100
99.5
98.5
97.5
95.5
93.5
91
88
84 79
150
7QC Tools
Pareto 200 175
75
Department
33 45
25 20
25
15
12
10
8
6
5
4
4
2
2
1
0
Nos.
Relative %
Cumulative %
Materials
66
33.0
33.0
2
Marketing
45
22.5
55.5
3
Plant Maintenance
20
10.0
65.5
4
Finance
15
7.5
73.0
5
Service
12
6.0
79.0
6
Production Engineering
10
5.0
84.0
7
Personnel
8
4.0
88.0
8
Information Systems
6
3.0
91.0
9
Stores
5
2.5
93.5
10
Research & Development
4
2.0
95.5
11
Others
4
2.0
97.5
12
Quality
2
1.0
98.5
13
Factory production
2
1.0
99.5
14
Manufacturing Planning
1
0.5
100.0
200
100
Quality
Factory production
Manufacturing Planning
Stores
Others
Information Systems
Research & Development
Service
Personnel
Finance
Production Engineering
Plant Maintenance
Materials
0
Dept
1
Q7T/PPT- 26
50 66
50
Data No. Of External Phone Calls Sl.No
55.5 100
In %
In nos
Calculate the cumulative % for individual
75
73 65.5
125
Marketing
STEP 4
100 100
99.5
98.5
97.5
95.5
93.5
91
88
84 79
150
7QC Tools
Sl.No
Pareto
Department
Nos.
Relative %
Cumulative %
66
33.0
33.0
45
22.5
55.5
20
10.0
65.5
15
7.5
73.0
1
Materials
2
Marketing
3
Plant Maintenance
4
Finance
5
Service
12
6.0
79.0
6
Production Engineering
10
5.0
84.0
7
Personnel
8
4.0
88.0
8
Information Systems
6
3.0
91.0
9
Stores
5
2.5
93.5
10
Research & Development
4
2.0
95.5
11
Others
4
2.0
97.5
12
Quality
2
1.0
98.5
13
Factory production
2
1.0
99.5
14
Manufacturing Planning
1
0.5
100.0
200
100
Q7T/PPT- 27
VITAL FEW TRIVIAL MANY
7QC Tools
Sl.No
Q7T/PPT- 28
Pareto
Department
Nos.
Relative %
Cumulative %
1
Materials
66
33.0
33.0
2
Marketing
45
22.5
55.5
3
Plant Maintenance
20
10.0
65.5
4
Finance
15
7.5
73.0
5
Others
60
27
100
200
100
7QC Tools
Pareto
180
150
In nos
120
90 66 54
60
45
30
20
15
Dept Q7T/PPT- 29
others
Finance
Plant Maintenance
Marketing
Materials
0
7QC Tools
Pareto
100
100
180
150
75
73
In nos
120
55.5 50
90 66 60
33
54 45
30
25 20
15
0
Dept Q7T/PPT- 30
others
Finance
Plant Maintenance
Marketing
Materials
0
Cumulative %
65.5
7QC Tools
Pareto 100
Vital Few
180
70 %
150
100
75
73
In nos
120 55.5 50 90 66 60
33
54 45
30
25 20
15 0
Dept
Q7T/PPT- 31
others
Finance
Plant Maintenance
Marketing
Materials
0
Cumulative %
65.5
7QC Tools
Pareto
Why pareto ? • To Clearly prioritise the magnitude of the problem. • To identify the vital few and trivial many problems. • To find 80/20 rule which states that 80% of the problems are created by 20% of the causes.
Q7T/PPT- 32
7QC Tools
Add examples from APC………..
Q7T/PPT- 33
7QC Tools
Data Collection Q4 ‘02 Final Failure Details Q 4' 02 F inal failure D etails SL#
Q 4 F in al F ailu re D etails 2500
100.00 95.5 95.12 94.64 93.98 93.28 90.56 91.70 92.58 90.00 88.16
2062 2000
80.00
75.97
70.00 1500
60.00 Cum % 50.00
Qty
O ct '02 N ov '02 D ec '02 Jan '03 Total % D P U C um % D esc ription 2062 6.38 75.97 1 S ec o n d P ass 520 710 73 759 331 1 .02 88.1 6 2 D efec tive 68 227 22 14 3 B roken C om p 6 48 6 5 65 0.20 90.56 4 M is inserted 1 22 1 7 31 0.1 0 91 .70 5 S kewed C om p 6 14 1 3 24 0.07 92.58 6 C om p M issing 15 0 0 4 1 9 0.06 93.28 7 O ut of toleranc e 8 7 0 4 1 9 0.06 93.98 8 N o / Low solder 8 9 0 1 1 8 0.06 94.64 9 Lifted 7 2 0 4 1 3 0.04 95.1 2 10 S horts 9 0 0 0 9 0.03 95.5 8612 14314 1185 12859 36970 Tested 7838 13219 1058 11978 34093 8.4 8.02 P assed
1000
40.00 30.00
500
20.00
331
10.00
65
31
24
19
19
18
13
9
3
4
5
6Failure7
8
9
10
0 1
Q7T/PPT- 34
2
0.00
7QC Tools
Pareto
Same problem, but different approach…
You have to cut down your house expenditure by 20% / month How will you do it ? Pareto
Q7T/PPT- 35
7QC Tools
Pareto
Make a check list of all the expenses in your home & the amount you spend on these expenses
Q7T/PPT- 36
7QC Tools
Pareto Sl.No
Q7T/PPT- 37
Expense
Amount
1
House Rent
3000
2
Electricity Bill
500
3
Water Bill
280
4
Cable TV Bill
210
5
News paper bill
120
6
Milkman
300
7
Maid servant
150
8
Groceries
2000
9
Entertainment & Lifestyle
1500
10
Travel
200
11
Educational
1500
12
Hospital
200
13
Insurance Premium
500
14
Loan repayment
15
Clothes
200
16
Petrol
1300
17
Others
300
0
7QC Tools
Pareto
Arrange these expenses & amounts in an order, with the highest expense being the first & lowest expense being the last
Q7T/PPT- 38
7QC Tools
Pareto Sl.No
Expense
Amount
1
House rent
3000
2
Groceries
2000
3
Entertainment
1500
4
Educational
1500
5
Petrol
1300
6
Electricity bill
500
7
Insurance premium
500
8
Milkman
300
9
Others
300
10
Water bill
280
11
Cable TV
210
12
Travel
200
13
Clothes
200
14
Hospital
200
15
Maid servant
150
16
News paper
120
17
Loan repayment
0 12260
Q7T/PPT- 39
7QC Tools
Pareto
Calculate the percentage contribution of each of these expenses. Percentage can be calculated by the formula Individual expense Total expense
Q7T/PPT- 40
X 100
7QC Tools Sl.No
Pareto Department
Nos.
Relative %
1
House rent
3000
24.47
2
Groceries
2000
16.32
3
Entertainment
1500
12.23
4
Educational
1500
12.23
5
Petrol
1300
10.6
6
Electricity bill
500
4.08
7
Insurance premium
500
4.08
8
Milkman
300
2.45
9
Others
300
2.45
10
Water bill
280
2.28
11
Cable TV
210
1.72
12
Travel
200
1.63
13
Clothes
200
1.63
14
Hospital
200
1.63
15
Maid servant
150
1.22
16
Newspaper
120
0.98
17
Loan repayment
0
0
12260
100
Q7T/PPT- 41
7QC Tools Sl.No
Q7T/PPT- 42
Pareto Department
Nos.
Relative %
Cumulative %
1
House rent
3000
24.47
24.47
2
Groceries
2000
16.32
40.79
3
Entertainment
1500
12.23
53.02
4
Educational
1500
12.23
65.25
5
Petrol
1300
10.6
75.85
6
Electricity bill
500
4.08
79.93
7
Insurance premium
500
4.08
84.01
8
Milkman
300
2.45
86.46
9
Others
300
2.45
88.91
10
Water bill
280
2.28
91.19
11
Cable TV
210
1.72
92.91
12
Travel
200
1.63
94.54
13
Clothes
200
1.63
96.17
14
Hospital
200
1.63
97.8
15
Maid servant
150
1.22
99.02
16
Newspaper
120
0.98
100
17
Loan repayment
0
0
100.0
12260
100
100
7QC Tools Sl.No
Q7T/PPT- 43
Department
Nos.
Relative %
Cumulative %
1
House rent
3000
24.47
24.47
2
Groceries
2000
16.32
40.79
3
Entertainment
1500
12.23
53.02
4
Educational
1500
12.23
65.25
5
Petrol
1300
10.6
75.85
6
Electricity bill
500
4.08
79.93
7
Insurance premium
500
4.08
84.01
8
Milkman
300
2.45
86.46
9
Others
300
2.45
88.91
10
Water bill
280
2.28
91.19
11
Cable TV
210
1.72
92.91
12
Travel
200
1.63
94.54
13
Clothes
200
1.63
96.17
14
Hospital
200
1.63
97.8
15
Maid servant
150
1.22
99.02
16
Newspaper
120
0.98
100
17
Loan repayment
0
0
100.0
12260
100
100
100 90 80 70 60 50 40 30 20 10 0
12000
Amount
10000 8000 6000 4000 2000
Expenses
Q7T/PPT- 44
O th er s
Pe tro l
na l Ed uc at io
en t
En te rta in m
G ro ce r ie s
Ho us e
R
en t
0
Cumulative %
7QC Tools
7QC Tools
Cause & effect diagram
Cause & Effect diagram
Q7T/PPT- 45
7QC Tools
Cause & effect diagram
Why Cause & Effect ? • To identify and systematically list the different causes that can be attributed to a problem (or an effect) • To identify the reasons why a process goes out of control • To decide which causes to investigate for process improvement.
Q7T/PPT- 46
7QC Tools
Cause & effect diagram
What is Effect ? EFFECT = A Result or an outcome EFFECT is What happens
Q7T/PPT- 47
7QC Tools
Cause & effect diagram
What is cause ? CAUSE = Reason or Factor contributing to the EFFECT CAUSE is WHY it happens
Q7T/PPT- 48
7QC Tools
Cause & effect diagram
The analysis of “why?” for “what?” is cause and effect diagram
Q7T/PPT- 49
7QC Tools
Cause & effect diagram In 1953, Kaoru Ishikawa, Professor of the University of Tokyo, used the Cause & effect diagram for the first time. A cause & effect diagram is also called a fish bone diagram since it looks like the skeleton of a fish.
Q7T/PPT- 50
7QC Tools
Cause & effect diagram Cause & Effect diagram derived from pareto Pareto chart
Cause-and-effect diagram
Q7T/PPT- 51
7QC Tools
Cause & effect diagram
Steps of making cause & effect diagram
Q7T/PPT- 52
7QC Tools
Cause & effect diagram Steps of making cause & effect diagram
Step 0 • Gather members for discussion • Clarify the problem to all members Step 1 • Conduct Brain storming session • List all possible causes Step 2 • Classify the causes into 4M • Draw Ist level Cause & Effect diagram Step 3 • Delete irrelavant causes Step 4 • Assign importance factor to the remaining causes Step 5 • Conduct why why analysis if required to find root causes Q7T/PPT- 53
7QC Tools
Cause & effect diagram
Step 1 List all the causes that have been suggested by team members as a part of brain storming.
What is brain storming ?
Q7T/PPT- 54
7QC Tools
Brainstorming is another tool which we use as a part of all the 7 QC tools
Q7T/PPT- 55
7QC Tools
Brain storming
BRAIN STORMING !
Q7T/PPT- 56
7QC Tools
Brain storming
BRAIN STORMING Brain storming is a technique to obtain creative ideas from a group of persons in a shortest possible time Brain storming plays an important role to build a cause and effect diagram
WHY
To identify the problem - to identify the causes To find solution
Q7T/PPT- 57
- to prevent problem
7QC Tools
Brain storming
BRAIN STORMING Brain storming can be conducted in two ways 1. Structured •
Every person in a group must give an idea as their turn arises.
•
Forces even shy people to participate.
•
Creates a certain amount of pressure to contribute.
Q7T/PPT- 58
7QC Tools
Brain storming
2. Unstructured • Group members simply give ideas as they come to mind. • Creates more relaxed atmosphere • Risks domination. Thumb rule : 5 – 15 minutes works well
Q7T/PPT- 59
7QC Tools
Brain storming
BRAIN STORMING SESSION • Let all the members speak freely and give ideas • Encourage wild ideas • “Quantity” rather than “Quality” ideas • Suspend judgment on “Good” or “Bad” • Ride on another’s ideas • Never criticize other persons’ opinions • Never prohibit a person from speaking • See the problem from different angles/facets • Write down all the viewpoints • List the cause/ideas • Think of the countermeasures to eliminate the causes • Leader/facilitator need to guide the members in generating ideas • Whenever necessary non – members can also be involved Q7T/PPT- 60
7QC Tools
Brain storming
WHY BRAIN STORMING?
TO IDENTIFY THE PROBLEM
TO IDENTIFY CRITICAL CAUSES TO FIND THE SOLUTION TO PREVENT THE PROBLEM
Q7T/PPT- 61
7QC Tools
Brain storming
BENEFITS OF BRAIN STORMING? •• Individual Individualis islimited limitedin ingenerating generatingideas ideasand andthat that group groupproduces producesmore moreideas ideas •• Ideas Ideasare areimproved improvedupon uponby bymembers members •• Presence Presenceof ofothers othersincreases increasescreativity creativity •• Pooling Poolingof ofideas ideasand andresources resourcesis ismade madepossible possibleby by coming comingtogether togetheras asaagroup group
Q7T/PPT- 62
7QC Tools
Cause & effect diagram
Step 2 Draw Cause & Effect diagram – Level 1 Classify the causes into 4M Sort out the relations among the causes & connect the sub causes to the main causes. The main causes should then be connected to the effect.
Q7T/PPT- 63
7QC Tools
METHOD
MATERIAL
Sub cause
PROBLEM
Sub-sub cause
MAN
MACHINE
CAUSES
Q7T/PPT- 64
EFFECT
7QC Tools
Cause & effect diagram
MAN
2
MACHINE
Fatigue
Imbalance
HEALTH
Concentration
Illness
Training
STABILITY
Instrument SPIRIT
Vibration
INSPECTION
Clamping
Attentiveness
SKILL
JIGS & FIXTURES
Method Experience
Location
Inspection
Degree of tightening SETTING
QUALITY Storage
FORM Placement on locator Feed
Shape
WORKING Spindle speed
Dimension
MATERIAL
Q7T/PPT- 65
METHOD
Dimensional Variation
7QC Tools
Step 3 Delete irrelavant causes
Q7T/PPT- 66
Cause & effect diagram
7QC Tools
Cause & effect diagram
MAN
2
MACHINE
Fatigue
Imbalance
HEALTH
Concentration
Illness
Training
STABILITY
Instrument SPIRIT
Vibration
INSPECTION
Clamping
Attentiveness
SKILL
JIGS & FIXTURES
Method Experience
Location
Inspection
Degree of tightening SETTING
QUALITY Storage
Dimensional Variation
FORM Placement on locator Feed
Shape
WORKING Spindle speed
Dimension
MATERIAL
METHOD
The EFFECT or PROBLEM is stated on the right side of the diagram and the major INFLUENCES or CAUSES are listed to the left. Q7T/PPT- 67
7QC Tools
Cause & effect diagram
Step 4 Evaluate the siginificance of each cause to the problem and assign importance factor Assign an importance to each factor, & mark the particularly important factors which seem to have a significant effect.
Q7T/PPT- 68
7QC Tools
Cause Verification
4M
Man
Cause
No focused training
Specification Functionwise training
No method to measure Skill matrix for operator's skills Method
Material
Q7T/PPT- 69
No OJT
each workmen Practical training at genba
Investigation
Generic
No skill matrix
No OJT
Workmen not trained in Need based
Common
specific jobs
training
module given
Module content is
Content should be specific need Theory based
academic oriented
based
Analysis
7QC Tools
Cause & effect diagram
Step 5 Do why why analysis for the significant causes Atleast ask why 3 times
Q7T/PPT- 70
7QC Tools
Cause & effect diagram Thorough investigation of causes
ASK WHY? 5 TIMES 5th Why
4th Why
C
Policies
Procedure D
2nd Why
3rd Why
People
Q7T/PPT- 71
1st Why
Plant
Why defects?
7QC Tools ‘WHY WHY’ Analysis Primary Phenomenon (Result)
Secondary
Cause
Tertier
Phenomenon (Result)
Cause Phenomenon (Result)
Examples :
Cause Phenomenon (Result)
- Cylinder does not operate smoothly Why
Answer
Action
Why is opertion not smooth?
Strainer clogged.
Clean strainer.
Why has strainer clogged?
Oil was dirty.
Drain oil and clean.
Why did oil get dirty?
Dirt enters tank.
Prevent scattering of chips and cutting fluid
Why does dirt get in?
Upper plate of tank has hole and gap. Plug hole and gap.
Why was hole made?
Repair error during maintenance work. Standardize repairs.
Q7T/PPT- 72
7QC Tools ‘WHY WHY’ Analysis
- Oil leaks from cylinder rod each time it operates. Why Why did it leak? Why was it cut? Why was it scratched? Why did chips get attached? Why is rod praced in that Why no cover?
Q7T/PPT- 73
Answer Cut in O-ring. Rod has scratch. Chip was scattered and attached on rod. Cylinder is located within scattering range of chips. Rod cover is not placed. Defective design and installation
Action Disassemble leaking part. Replace O-ring. Remove scratch. Take measure to prevent chips from scattering Change cylinder position Install cover. Standardize design and installation.
7QC Tools
Cause & effect diagram
Guidelines • Special effort should be made to identify as many causes as possible • The ideal method to identify as many causes as possible would be by brainstorming with the team members. • All the ideas/causes suggested by members during the brainstorming session should be noted however insignificant they may initially appear. Brainstorming is a session specially meant for free flow of ideas.
Q7T/PPT- 74
Remember
7QC Tools
METHOD
MATERIAL
Sub cause
Sub-sub cause
MAN
MACHINE
CAUSES
Q7T/PPT- 75
EFFECT
7QC Tools
Non-standard HANDLING
COPYING PAPER
Not understanding the defect codes/ communicating defects Paper jam Wrong paper not cleared usage properly Lack of Paper with stables Untrained personnel knowledge handling the machine Supply from various sources Nominated persons Non-standard not handling
Party removed
Dust accumulation
Frequent changes
Location No cleaning Heavy usage
No stabilizer
High fluctuation
MACHINE Q7T/PPT- 76
Over consumption Paper shortage No communication
Serviced by unauthorized persons Improper service No periodical service
Power Limited machines
Not using specified quality of paper
Specified toner not filled Lack of knowledge
PROCESS CONSUMABLES
POOR QUALITY OF XEROX COPIES
7QC Tools
Cause & effect diagram
1 Effect
Causes Q7T/PPT- 77
7QC Tools
A combination of Pareto diagram & cause and effect diagram is an ideal way to arrive at the main problem & its causes. Take the biggest problem from the pareto diagram & put it on the right side in the cause & effect diagram. Derive the causes for the same.
Q7T/PPT- 78
7QC Tools
Examples from APC………..
Q7T/PPT- 79
7QC Tools
METHOD Improper tools
MATERIAL
PROCESS
Data Mixed process & Original
SCRAP
Handling Pro not defined. No process flow Identification and Segregation Not done.
Improper Storage In racks . Machine rejections are high.
Program /Nozzle error No plan for Feeder maintenance Q7T/PPT- 80
No Alarms for M/C Board Jam.
MACHINE
Improper /Movement High Rej in M/C. Improper Storage Incoming material.
Improper Handling No Awareness Inadequate Training Scrap Disposal Training /Procedure is inadequate
MAN
7QC Tools
METHOD Improper tools
MATERIAL
PROCESS
Data Mixed process & Original
SCRAP
Handling Pro not defined. No process flow Identification and Segregation Not done.
Improper Storage In racks . Machine rejections are high.
Program /Nozzle error No plan for Feeder maintenance Q7T/PPT- 81
No Alarms for M/C Board Jam.
MACHINE
Improper /Movement High Rej in M/C. Improper Storage Incoming material.
Improper Handling No Awareness Inadequate Training Scrap Disposal Training /Procedure is inadequate
MAN
7QC Tools
Ishikawa Diagram MAN
METHOD
Operator absenteeism Operator Skill (Prep of Heat sink)
High Touch up defects before ICT Imbalance flow of production
Board Flow from Wave to ICT
High DPU
M/c Cycle time improvement Tab & radial BHS problem
Low Productivity GSM error Spindle up
Battery Charging
ICT Downtimes and Second pass
IC-9 Screening
Scratches High Rejection on plastic parts
Serial Number Screening
MACHINE
MATERIAL
Flow & Black Mark Printing Defect
Q7T/PPT- 82
7QC Tools
Stratification
Stratification
Q7T/PPT- 83
7QC Tools
Q7T/PPT- 84
Stratification
7QC Tools
Stratification
Stratification 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.
Q7T/PPT- 85
7QC Tools
Why Stratification? To ascertain the difference between different categories and to analyse the reasons behind abnormal distribution. To obtain clues for identifying the causes
Q7T/PPT- 86
Stratification
7QC Tools
Stratification
Case study Problem : Increased Inventory Raw Material
Total Inventory
Components
Work in process
Q7T/PPT- 87
sheets Bars Tubes Imports Proprietary pressings Fasteners Rubber Rubber Bearings Castings Shop wise Assy wise Sub-Assy wise Stage wise Machine wise Rt Rejections
Tubes Proprietary Fasteners Bearings Shop wise Sub-Assy wise
7QC Tools
Stratification
Case study 2 Problem : More No. of Accidents Let us stratify the the data regarding the accidents
Q7T/PPT- 88
7QC Tools
Stratification STATISTICS
Q7T/PPT- 89
REPORTABLE ACCIDENTS
:
08
NON-REPORTABLE ACCIDENTS
:
33
NEAR MISS INCIDENTS
:
21
LOST TIME INJURIES
:
41
MANDAYS LOST
:
187
Rep.acct. for
– Operator not reporting back to duty more than 48hrs
Non-reportable acct. beyond less than 48 hrs
– Operator disablement extending the day of shift but
Lost time injury
– Reportable + Non-reportable
7QC Tools
Stratification
ANALYSIS –REPORTABLE ACCIDENT Total no of reportable accident :
Q7T/PPT- 90
8
7QC Tools
Stratification ACCORDING TO CATEGORY
Contract Labour (1) 13%
Regular Employee (4) 49%
Total no.of Reportable accidents : 8
Q7T/PPT- 91
Temp.workman (3) 38%
7QC Tools
Stratification ACCORDING TO PROBLEM
Adjusting/Cleaning/Loading/Unloading while M/C running
6
Wrong handling of material handling equipment
2
Hit against object
0
Hit by objects/Fallen objects
0
others
0
Fall from Height
0
Fall from Two wheeler
0
Contact with chemical
0
wrong assembly
0
0
1
2
3
4
No of Accidents
Total no.of Reportable accidents : 8
Q7T/PPT- 92
5
6
7
7QC Tools
Stratification ACCORDING TO BODY PARTS INJURED
Leg (2) 25%
Hand (1) 13%
Total no.of Reportable accidents : 8
Q7T/PPT- 93
Finger (5) 62%
7QC Tools
Stratification ACCORDING TO PLANT
Others (1) 13%
Plant-1 (0) 0% Plant-2 (3) 37%
Sp. Wh (1) 13%
R & D (1) 13% Plant-3 (2) 24%
Total no.of Reportable accidents : 8
Q7T/PPT- 94
7QC Tools
Stratification ACCORDING TO UNIT
No.of accidents
2
1
PLANT- 2
1
1
1
0
0 FAB
ENG UNIT
Total no.of Reportable accidents : 8
Q7T/PPT- 95
PAINT
VECH UNIT
0 STORES
0 PLATING
7QC Tools
Stratification ACCORDING TO SHIFT
5
No.of accidents
4
4
3 2
2
2
1 0
0 I II Total no.of Reportable accidents : 8
Q7T/PPT- 96
III
0 GEN
OT
7QC Tools
Stratification ACCORDING TO MONTH
4 3 2 1
Q7T/PPT- 97
1
M
A
RC
RY UA FE BR A
BE R EM DE C
EM
H
0
BE R
0 NO V
A UG US T
Total no.of Reportable accidents : 8
0 O C TO BE R
0
BE R
0
SE PT EM
0
JU LY
A M
A
PR IL
0
Y
0
JU NE
1
1
RY
2
JA NU A
No.of accidents
3
7QC Tools
Stratification ACCORDING TO FAULT
No.of accidents
4 3
3
3 2
2 1 0 OPERATORS FAULT
SUPERVISORY FAULT
Total no.of Reportable accidents : 8
Q7T/PPT- 98
SYSTEM AND ENVIRONMENT FAULT
7QC Tools
The data has been stratified 1. According to employee category 2. According to phenomenon 3. According to body parts injured 4. According to plant a. According to unit 5. According to shift 6. According to month 7. According to fault
Q7T/PPT- 99
Stratification
7QC Tools
Graph&control charts
Graph & Control charts
Q7T/PPT- 100
7QC Tools
Graph&control charts
Graph What is Graph? When there are more than 2 interrelated data sets,you write the datasets on a graph so as to clearly define the relationships. Why Graph? The details of the data should be • Correctly understood • In their entirety • With just a one look – Pictorial representation A picture is worth of thousand words Q7T/PPT- 101
7QC Tools
Graph&control charts
Graph Types of Graphs & Its application Bar graphs,line graphs, pie charts, and band graphs. There are also other specialty graphs such as radar charts, Z charts and area graphs Applications
Q7T/PPT- 102
To understand relative sizes of numbers
To understand trends over time
To understand percent-ages of totals
7QC Tools
Graph&control charts
Pie chart - Composition of sales turnover 2001-02 Export Sales 1%
Spare parts sales 6%
Other income 1%
Vehicle sales 92%
Pie charts are used to show percentages or proportions of different components of a specific item. Q7T/PPT- 103
7QC Tools
Graph&control charts
Bar chart - Sales performance Plan for 2002-03
Rs Million x 100 300
262
250 162
200
104
100
0
Q7T/PPT- 104
194
133
150
50
184
62 14
90-91
17
19
27
91-92
92-93
93-94
83
41
94-95
95-96
96-97
97-98
98-99
99-00
00-01
'01-02
'02-03
Bar charts are used for comparing quantities between persons, regions, time intervals etc.
7QC Tools
Graph&control charts
Line chart - Hourly output of Workmen 46
45
45
No. of workmen
44
43
43
42
42
42
Mar
Apr
May
42 41
40
40 39 38 37 Jan
Q7T/PPT- 105
Feb
Line graphs are used to depict change or variation over time.
Jun
7QC Tools
Graph&control charts
How to draw graphs? •
Select the type of chart or graph most suitable for the type of data.
•
Decide the units and scale of items to be shown on X-axis and Yaxis
•
Fill the information on the graph
•
Join the required points to complete lines or bars.
•
Colour or shade the lines or bars to distinguish between different groups or classes.
•
Provide appropriate title.
Q7T/PPT- 106
7QC Tools
Histogram
To add examples from APC
Q7T/PPT- 107
7QC Tools
Results Productivity improvement 600
After Units produced / Shift
500
522
Before 370
400
277
300
246
397
278
208 200 100 0
OCT
NOV
DEC
JAN Month
Q7T/PPT- 108
FEB
MARCH
APRIL
7QC Tools
Results ICT FINAL DPU
DPU Trend for Cerror Torre 30
Before 25
20.4
% DPU
20
15
23.9
23.8
13.9 12.1
10
12 11.9 8.2 7.4
5
11.6
7.3
7.4
4.4
4.2
10.3 6.5 3.8
OCT
NOV
DEC
JAN
FEB
MAR
APRIL
ICT
13.9
12.1
11.9
8.2
7.3
7.4
6.5
FINAL
9.9 23.8
8.3 20.4
12 23.9
7.4 15.6
4.4 11.7
4.2 11.6
3.8 10.3
DPU Q7T/PPT- 109
11.7
9.9 8.3
0
After
15.6
7QC Tools
Southern chips Problem trend
April Scratches 22%
25%
Printing missing Ckt Brkr Broken
16%
11% 26%
Sleeve not put Wire interchange Wire not connected
Q7T/PPT- 110
7QC Tools
Histogram
Histogram
Q7T/PPT- 111
7QC Tools
Histogram is an important diagnostic tool which gives a ‘Birds –eye-view’ of the variation in a data set. It is nothing but a frequency distribution chart. It shows the distribution of data
Q7T/PPT- 112
7QC Tools
Histogram
• In quality control, we try to discover facts by collecting data & then take necessary action based on those facts. • The data is not collected as an end in itself, but as a means of finding out the facts behind the data.
Data FACTS
Q7T/PPT- 113
7QC Tools
• For example, consider a sampling inspection. We take a sample from a lot, carry out measurements on it, and then decide whether we should accept the whole lot or not. Here our concern is not the sample itself, but the quality of the whole lot. The totality of items under consideration is called the population.
Q7T/PPT- 114
Histogram
7QC Tools
• The data obtained from a sample serves as a basis for a decision on the population. • The larger the sample size is, the more information we get about the population. • But an increase of sample size also means an increase in the amount of data
Q7T/PPT- 115
Histogram
7QC Tools
Histogram
• It becomes difficult to understand the population from these data even when they are arranged into tables. • In such a case we need a method which will enable us to understand the population at a glance. A histogram answers our needs.
Q7T/PPT- 116
7QC Tools
Histogram
What is histogram ? Histogram shows a bar chart of accumulated data and provides the easiest way to evaluate the distribution of data . The horizontal axis shows the values of the characteristics, with the region between the largest value and smallest value being broken into several smaller spaces. The sizes of the vertical bars reflects the number of data that fall into these spaces.
Q7T/PPT- 117
7QC Tools
Histogram
How to make a histogram? Let us make a histogram using an example. Example: To investigate the distribution of the diameters of steel shafts produced in the grinding process, the diameters of 90 shafts are measured as shown in the table.
Q7T/PPT- 118
7QC Tools
Histogram
Diameter after grinding Sample
Results of Measurement
Number 1 - 10
2.51
2.517
2.522
2.522
2.51
2.511
2.519
2.532
2.543
2.525
11 - 20
2.527
2.536
2.506
2.541
2.512
2.515
2.521
2.536
2.529
2.524
21 - 30
2.529
2.523
2.523
2.523
2.519
2.528
2.543
2.538
2.518
2.534
31 - 40
2.52
2.514
2.512
2.534
2.526
2.53
2.532
2.526
2.523
2.52
41 - 50
2.535
2.523
2.526
2.525
2.532
2.522
2.502
2.53
2.522
2.514
51 - 60
2.533
2.51
2.542
2.524
2.53
2.521
2.522
2.535
2.54
2.528
61 - 70
2.525
2.515
2.52
2.519
2.526
2.527
2.522
2.542
2.54
2.528
71 - 80
2.531
2.545
2.524
2.522
2.52
2.519
2.519
2.529
2.522
2.513
81 - 90
2.518
2.527
2.511
2.519
2.531
2.527
2.529
2.528
2.519
2.521
Q7T/PPT- 119
7QC Tools
CONSTRUCTING A HISTOGRAM STEPS 1. Collect data 2. Determine the largest value & smallest value 3. Obtain the range R (The range is the smallest value in the set of data subtracted from the largest value 4. Divide the range value in to certain number of classes referred to as K 5. Determine the class width, H = R / K 6. Divide the value of class boundary 7. Construct a frequency table, based on the values compiled 8. Construct Histogram based on the frequency table Q7T/PPT- 120
7QC Tools CASE STUDY STEP 1
Collect data 9.9 9.8 9.7 10.2 9.9 9.3 9.0 10.0 9.5 9.6 10.3 9.5 9.9 9.9
Q7T/PPT- 121
Period Material UOM Thickness
9.3 9.8 9.4 10.1 10.7 10.2 9.5 9.7 9.7 9.4 9.6 9.5 10.4 10.2
10.2 10.1 9.6 9.8 9.3 9.2 9.7 9.4 10.6 10.1 9.7 9.8 9.3 9.8
9.4 10.1 9.9 9.7 10.0 9.8 10.1 10.3 10.3 9.9 9.9 9.7 9.7 9.8 9.8 9.4 9.5 10.1 9.5 10.1 9.7 10.1 9.9 9.2 9.6 10.2 9.3 9.6 N = 125
9.6 9.8 9.9 10.0 9.8 9.9 9.8 9.6 10.0 10.2 9.8 10.0 9.7 9.5
10.1 10.0 10.4 9.8 9.5 9.5 9.6 10.3 10.1 9.5 10.0 9.7 9.7 10.7
9.9 9.9 10.1 10.2 9.8 9.8 9.3 10.0 9.8 9.8 9.7 10.0 9.7 9.6
: wk no. 15 to 20 : ms flange collar : mm : 9 mm + 1.5 mm
9.8 9.6 10.0 10.7 9.4 9.4 9.7 9.8 9.3 9.3 10.0 9.7 10.7
7QC Tools
CASE STUDY STEP 2
9.9 9.8 9.7 10.2 9.9 9.3 9.0 10.0 9.5 9.6 10.3 9.5 9.9 9.9
Q7T/PPT- 122
DETERMINE THRE LARGEST AND SMALLEST VALUE 9.3 9.8 9.4 10.1 10.7 10.2 9.5 9.7 9.7 9.4 9.6 9.5 10.4 10.2
10.2 10.1 9.6 9.8 9.3 9.2 9.7 9.4 10.6 10.1 9.7 9.8 9.3 9.8
9.4 9.9 10.0 10.1 10.3 9.9 9.7 9.8 9.5 9.5 9.7 9.9 9.6 9.3
10.1 9.7 9.8 10.3 9.9 9.7 9.8 9.4 10.1 10.1 10.1 9.2 10.2 9.6
9.6 9.8 9.9 10.0 9.8 9.9 9.8 9.6 10.0 10.2 9.8 10.0 9.7 9.5
10.1 10.0 10.4 9.8 9.5 9.5 9.6 10.3 10.1 9.5 10.0 9.7 9.7 10.7
9.9 9.9 10.1 10.2 9.8 9.8 9.3 10.0 9.8 9.8 9.7 10.0 9.7 9.6
9.8 9.6 10.0 10.7 9.4 9.4 9.7 9.8 9.3 9.3 10.0 9.7 10.7
N = 125 Minimum Maximum 9.3 10.2 9.6 10.1 9.4 10.4 9.8 10.7 9.3 10.7 9.2 10.2 9.0 9.8 9.4 10.3 9.5 10.6 9.3 10.2 9.6 10.3 9.2 10.0 9.3 10.7 9.3 10.7 9.0 10.7
7QC Tools
CASE STUDY
STEP 4
Divide the ‘R’ in to No. Of Classes, referred to as ‘K’ 125 data points would be broken down in to 7 – 12 classes. Method – 2
Method - 1 No.of data points
No. of classes
Under 50
5–7
50 – 100
6 – 10
100 – 250
7 – 12
Over 250
10 - 20
No. Of Classes – K = √N where, N = No. Of sample For example, if N = 125 K = √125 = 11
Let us use K = 10 classes Q7T/PPT- 123
7QC Tools
CASE STUDY STEP 3
Obtain the range of R
Maximum value – Minimum Value = R 10.7 – 9.0 = 1.7 R = 1.7
Q7T/PPT- 124
7QC Tools
CASE STUDY STEP 5
Determine the class width ‘H’ R
(Range)
K
(# of classes)
= H
1.7 = 0.17 10 Can be rounded off to 0.20
Q7T/PPT- 125
7QC Tools
CASE STUDY STEP 6
Divide the value of class boundary
For simple determination of class boundaries, take the smallest individual measurement in the data set. Use this number or round to the next appropriate lowest number. This will be lower end point for our first class boundary. In our example this would be 9.0. Now take this number and add the class width to it, 9.00 + 0.20. But it is essential to fix class boundaries in such way that every observed reading will fit in to ‘one’ and ‘only’ class. Therefore, we may choose the class boundaries with one decimal place more than the observed readings. For example, if the observations are in one decimal, the class boundaries will be in two decimals and so on. For our case study, it will be 8.95 + 0.20 = 9.15 Finally, consecutively add the class width, to the lowest class boundary until the correct number of classes, approximately 10 and containing the range of all our numbers is obtained. Q7T/PPT- 126
7QC Tools
CASE STUDY STEP 7
Construct a frequency table
Class Class Midpoint # Boundaries
Q7T/PPT- 127
Frequency
Total
1
8.95-9.15
9.05
1
2
9.15-9.35
9.25
9
3
9.35-9.55
9.45
16
4
9.55-9.75
9.65
27
5
9.75-9.95
9.85
29
6
9.95-10.5
10.05
26
7
10.5-10.35
10.25
11
8
10.35-10.55
10.45
1
9
10.55-10.75
10.65
5
10
10.75-10.95
10.85
0
7QC Tools
CASE STUDY
Frequency
STEP 8
Construct Histogram
35 30 25 20 15 10 5 0
USL
8.95 9.15 9.35 9.55 9.75 9.95 10.15 10.35 10.55 10.75 Thickness in mm
The specification for the thickness characteristic is 7.5 to 10.5, with a target of 9. The above Histogram indicates the process is targeted high and that 3% may be above the upper specification limit. Q7T/PPT- 128
7QC Tools
HISTOGRAM
Right & Left symmetrical
Having two peaks
Q7T/PPT- 129
Slopping the right
Having a cut end
Having extraordinarily high value in the end internal
Slopping to the left
Having an isolated peak
7QC Tools
200 150 100 50 0
Histogram - Daily Example Height of 100 men
Average response time to patient rings (1st shift) # Of Men
# Of Responses
Histogram – Administration/Service Example
40 30 20 10 0 63
1 2 3 4 5 6 7 8 9 1 Minutes
Frequency
67
69
Height (inches) Histogram-Manufacturing Print Density
8 6 4 2 0 0.6
0.8
0.1
1.2
Block density of print Q7T/PPT- 130
65
1.4
71
7QC Tools
Histogram
Application To analyze processes and discover items to be improved To research process capability To control the process (in a time series) To verify effects of an improvement
Q7T/PPT- 131
7QC Tools
Histogram
Uses of Histogram A Histogram can be used: • To display large amounts of data values in a relatively simple chart form. • To tell relative frequency of occurrence. • To easily see the distribution of the data. • To see if there is variation in the data. • To make future predictions based on the data.
Q7T/PPT- 132
7QC Tools
Scatter diagram
Scatter diagram
Q7T/PPT- 133
7QC Tools
Scatter diagram
Scatter diagram
In actual practice, it is often essential to study the relation of two corresponding data types For example, to what extent will the dimension of a machined part be varied by the change in the speed of a lathe?
Q7T/PPT- 134
7QC Tools
Scatter diagram
To study the relation of two variables such as the speed of the lathe & the dimension of the part we can use what is called a Scatter diagram.
Q7T/PPT- 135
7QC Tools
Scatter diagram
The two variables we will deal with are: a) A quality – characteristic & a factor affecting it, b) Two related quality characteristics, or c) Two factors relating to a single quality characteristic. Let’s consider the steps in making a scatter diagram
Q7T/PPT- 136
7QC Tools
Examples of such relationships Speed Vs Mileage Cutting speed Vs Tool life Etc……
Q7T/PPT- 137
Scatter diagram
7QC Tools
Scatter diagram
Step 1 Collect paired data (x,y) between which you want to study the relations & arrange the data in a table. It is desirable to have at least 30 pairs of data.
Q7T/PPT- 138
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Scatter diagram
Step 2 Find the maximum & minimum values for both x & y. Decide the scales of horizontal & vertical axes so that both the lengths become approximately equal, then the diagram will be easier to read. Keep the number of unit graduations between 3 to 10 for each axis & use round numbers to make it easier to read.
Choosing units that express the range of the x and y values, draw an x scale along the horizontal axis and a y scale along the vertical axis.
=
Q7T/PPT- 139
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Scatter diagram
Step 3 Plot the data on the section paper. Step 4 Enter all necessary items. Make sure that the following items are included so that anyone besides the maker of the diagram can understand at a glance: a) Title of the diagram b) Time interval c) Number of pairs of data d) Title & units of each axis e) Name (etc) of the person who made the diagram Q7T/PPT- 140
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Scatter diagram
Example A manufacturer of plastic tanks who made them using the blow moulding process encountered problems with defective tanks that had thin tank walls. It was suspected that the variation in air pressure, which varied from day to day, was the cause of the defective thin walls. The table shows data on blowing pressure & percent defective. Let us draw a scatter diagram using this data according to the steps given previously.
Q7T/PPT- 141
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Q7T/PPT- 142
Scatter diagram Data of blowing air pressure & percent defective of plastic tank Date Air pressure Percent (kgf/cm2) Defective Oct-01 8.6 0.889 2 8.9 0.884 3 8.8 0.874 4 8.8 0.891 5 8.4 0.874 6 8.7 0.886 7 9.2 0.911 8 8.6 0.912 9 9.2 0.895 10 8.7 0.896 11 8.4 0.894 12 8.2 0.864 13 9.2 0.922 14 8.7 0.909 15 9.4 0.905 16 8.7 0.892 17 8.5 0.877 18 9.2 0.885 19 8.5 0.866 20 8.3 0.896 21 8.7 0.896 22 9.3 0.928 23 8.9 0.886 24 8.9 0.908 25 8.3 0.881 26 8.7 0.882 27 8.9 0.904 28 8.7 0.912 29 9.1 0.925 30 8.7 0.872
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Scatter diagram
Step 1 As seen in the table, we have 30 pairs of data. Step 2 In this example, let blowing air pressure be indicated by X (horizontal axis), & percent defective by Y (vertical axis). Then, The maximum value of X: Xmax = 9.4 (kgf/cm2) The minimum value of X : Xmin = 8.2 (kgf/cm2) The maximum value of Y: Ymax = 0.928 (%) The minimum value of Y : Ymin = 0.864 (%)
Q7T/PPT- 143
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Scatter diagram
We mark off the horizontal axis in 0.5(kgf/cm2) intervals, from 8.0 to 9.5 (kgf/cm2) and the vertical axis in0.01(%) intervals, from 0.85 to 0.93(%) Step 3 Plot the data.
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Scatter diagram
0.93 0.92 0.91 0.9 0.89 0.88 0.87 0.86 0.85 8 Q7T/PPT- 145
8.5
9
9.5
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Scatter diagram
Step 4 Enter the time interval of the sample obtained (oct.1 – oct 30) number of samples (n = 30), horizontal axis (blowing air pressure [kgf/cm2]), vertical axis (percent defective [%]), and title of diagram (scatter diagram of blowing air pressure & percent defective). (Oct 1 – Oct 30)
Percentage defective
0.93
n=3 0
0.92 0.91 0.9 0.89 0.88 0.87 0.86 0.85 8
Q7T/PPT- 146
8.5
9
Blowing air pressure
9.5
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Scatter diagram
How to read scatter diagrams ? You can grasp the correlation between pairs of data just by looking at the shape of a scatter diagram. 5 examples are given below
Q7T/PPT- 147
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Scatter diagram
Positive correlation 35 30 25 20 15 10 5 0
Series1
0
5
10
15
20
If y increases with x or the vice versa, then x and y are positively correlated.
Q7T/PPT- 148
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Scatter diagram
Negative correlation 350 300 250 200 150 100 50 0
Series1
0
100
200
300
400
If y decreases as x increases, then the two types of data are negatively correlated. Q7T/PPT- 149
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Scatter diagram
No correlation 700 600 500 400 300 200 100 0
Series1
0
100
200
300
400
If no significant relationship is apparent between x and y, then the two data types are not correlated. Q7T/PPT- 150
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Scatter diagram
500
40
400
30 Series1
20
300
10
100
0
0
0
5
10
15
20
Positive correlation may be present
Q7T/PPT- 151
Series1
200
0
100
200
300
400
Negative correlation may be present
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Let us do an exercise ! Let us say you are simply not satisfied with the marks that your younger brother/sister is scoring. So you want him/her to study more. But does studying more really help? How to find out?
Q7T/PPT- 152
Scatter diagram
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Scatter diagram
Percentage of marks
Try a scatter diagram !
90 80 70 60 50 0.5 1.0 1.5 2.0 2.5
No. of hours of study/day
Q7T/PPT- 153
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Q7T/PPT- 154
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