7qc Tools Test

7QC Tools

Q7T/PPT- 1

7 QC TOOLS7 QC TOOLS

7QC Tools

Q7T/PPT- 2

Types of 7QC toolsCheck SheetCheck Sheet

Pareto DiagramPareto Diagram

Cause & Effect diagramCause & Effect diagram

StratificationStratification

Scatter DiagramScatter Diagram

Graph &Control chartsGraph &Control charts

HistogramHistogram

7 QC Tools7 QC Tools

Types

7QC Tools

Q7T/PPT- 3

Check sheetCheck sheetCheck sheet

7QC Tools

Q7T/PPT- 4

What is a check sheet?

Why is a check sheet necessary?

Check sheet

7QC Tools

Q7T/PPT- 5

Check sheets are forms used for

• standardizing

• checking results of work

• verifying and collecting data

Check sheet

Check sheet

7QC Tools

Q7T/PPT- 6

Check Sheet

Measured Data

Measured Data

Counted Data

Counted Data

Primary Data

Primary Data

Point Scale Data

Point Scale Data

Ordered Data

Ordered Data

Indiscrete value such as height, weight, length, time & temp., Etc.Indiscrete value such as height,

weight, length, time & temp., Etc.

Discrete value such as no. Of recording errors, no. of Item sold

& Rejections etc.

Discrete value such as no. Of recording errors, no. of Item sold

& Rejections etc.

YES / NO or √ / X - Type

YES / NO or √ / X - Type

1st, 2nd Order …Very Good, Good, No Good

… - Type

1st, 2nd Order …Very Good, Good, No Good

… - Type

1 Point, 2 Point … etc.

1 Point, 2 Point … etc.

Types of Check SheetCheck sheet

7QC Tools

Q7T/PPT- 7

Defect check sheet

Check sheet

Example of check sheet

Month ,dayComponent

12345678

9

10

4/1 2 3 4

No. of No. of defectsdefects

7QC Tools

Q7T/PPT- 8

• 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

How to prepare check sheets?

7QC Tools

Q7T/PPT- 9

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

Check points for check sheets preparationCheck sheet

7QC Tools

Q7T/PPT- 10

Pareto diagramPareto diagram

Pareto

7QC Tools

Q7T/PPT- 11

Do you remember this? (14th March 2001 - Eden gardens )

Pareto

7QC Tools

Q7T/PPT- 12

Do you remember this? (14th March 2001 - Eden gardens )

Pareto

7QC Tools

Q7T/PPT- 13

Now let’s look at the second innings score board:IndiaSS Das hit wicket b Gillespie 39S Ramesh c ME Waugh b Warne 30VVS Laxman c Ponting b McGrath 281SR Tendulkar c Gilchrist b Gillespie 10SC Ganguly c Gilchrist b McGrath 48R Dravid run out 180N R Mongia b McGrath 4Zaheer Khan not out 23Harbhajan Singh not out 8

Total 657

Pareto

7QC Tools

Q7T/PPT- 14

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

Pareto

7QC Tools

Q7T/PPT- 15

AustraliaM Hayden lbw b Tendulkar 67M Slater c Ganguly b Harbhajan 43J Langer c Ramesh b Harbhajan 28M Waugh lbw b Raju 0S Waugh c Sub B Harbhajan 24R Ponting c Das b Harbhajan 0A Gilchrist lbw b Tendulkar 0J Gillespie c Das b Harbhajan 6S Warne lbw b Tendulkar 0M Kasprowicz not out 13G McGrath lbw b Harbhajan 12

Total 212

Pareto

7QC Tools

Q7T/PPT- 16

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

Pareto

7QC Tools

Q7T/PPT- 17

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

Pareto

7QC Tools

Q7T/PPT- 18

• 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”

Pareto

Pareto

7QC Tools

Q7T/PPT- 19

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.

Pareto

7QC Tools

Q7T/PPT- 20

“Get to the biggest problems first”

‘Solve the vital few’

Pareto

7QC Tools

Q7T/PPT- 21

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.

7QC Tools

Q7T/PPT- 22

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%)

66

45

20 15 12 10 8 6 5 4 4 2 2 1

33

55.5

65.5

7379

8488

91 93.5 95.5 97.5 98.5 99.5 100

0

25

50

75

100

125

150

175

200

Mat

eria

ls

Mar

ketin

g

Pla

ntM

aint

enan

ce

Fina

nce

Ser

vice

Pro

duct

ion

Eng

inee

ring

Per

sonn

el

Info

rmat

ion

Sys

tem

s

Sto

res

Rese

arch

&D

evel

opm

ent

Oth

ers

Qua

lity

Fact

ory

prod

uctio

n

Man

ufac

turin

gP

lann

ing

Dept

In n

os

0

25

50

75

100

In %

Pareto

Creating a Pareto Diagram

Steps

7QC Tools

Q7T/PPT- 23

Data collection through check sheetPeriod : Week No. 45 To 50No. Of External Phone Calls

4Others146Information & Systems134Research & Development1215Finance1166Materials108Personnel95Stores81Manufacturing Planning72Factory production620Plant Maintenance545Marketing412Service32Quality 210Production Engineering 1

No. Of cells regd.DepartmentSl.No

STEP 1 66

45

20 15 12 10 8 6 5 4 4 2 2 1

33

55.5

65.5

7379

8488

91 93.5 95.5 97.5 98.5 99.5 100

0

25

50

75

100

125

150

175

200

Mat

eria

ls

Mar

ketin

g

Pla

ntM

aint

enan

ce

Fina

nce

Ser

vice

Pro

duct

ion

Eng

inee

ring

Per

sonn

el

Info

rmat

ion

Sys

tem

s

Sto

res

Rese

arch

&D

evel

opm

ent

Oth

ers

Qua

lity

Fact

ory

prod

uctio

n

Man

ufac

turin

gP

lann

ing

Dept

In n

os

0

25

50

75

100

In %

Pareto

7QC Tools

Q7T/PPT- 24

200

1Manufacturing Planning142Factory production132Quality124Others114Research & Development105Stores96Information Systems88Personnel710Production Engineering 612Service515Finance420Plant Maintenance345Marketing266Materials1

No. Of cells reqd.DepartmentSl.No

66

45

20 15 12 10 8 6 5 4 4 2 2 1

33

55.5

65.5

7379

8488

91 93.5 95.5 97.5 98.5 99.5 100

0

25

50

75

100

125

150

175

200

Mat

eria

ls

Mar

ketin

g

Pla

ntM

aint

enan

ce

Fina

nce

Ser

vice

Pro

duct

ion

Eng

inee

ring

Per

sonn

el

Info

rmat

ion

Sys

tem

s

Sto

res

Rese

arch

&D

evel

opm

ent

Oth

ers

Qua

lity

Fact

ory

prod

uctio

n

Man

ufac

turin

gP

lann

ing

Dept

In n

os

0

25

50

75

100

In %

Pareto

STEP 2 Arrange data in the descending orderNo. Of External Phone Calls

7QC Tools

Q7T/PPT- 25

2000.51.01.02.02.02.53.04.05.06.07.510.022.533.0

Relative %


Nos.DepartmentSl.No

66

45

20 15 12 10 8 6 5 4 4 2 2 1

33

55.5

65.5

7379

8488

91 93.5 95.5 97.5 98.5 99.5 100

0

25

50

75

100

125

150

175

200

Mat

eria

ls

Mar

ketin

g

Pla

ntM

aint

enan

ce

Fina

nce

Ser

vice

Pro

duct

ion

Eng

inee

ring

Per

sonn

el

Info

rmat

ion

Sys

tem

s

Sto

res

Rese

arch

&D

evel

opm

ent

Oth

ers

Qua

lity

Fact

ory

prod

uctio

n

Man

ufac

turin

gP

lann

ing

Dept

In n

os

0

25

50

75

100

In %

Pareto

STEP 3 Calculate the relative % for individualNo. Of External Phone Calls

7QC Tools

Q7T/PPT- 26

100200100.099.598.597.595.593.591.088.084.079.073.065.555.533.0

Cumulative %

0.51.01.02.02.02.53.04.05.06.07.510.022.533.0

Relative %


Nos.DepartmentSl.No

66

45

20 15 12 10 8 6 5 4 4 2 2 1

33

55.5

65.5

7379

8488

91 93.5 95.5 97.5 98.5 99.5 100

0

25

50

75

100

125

150

175

200

Mat

eria

ls

Mar

ketin

g

Pla

ntM

aint

enan

ce

Fina

nce

Ser

vice

Pro

duct

ion

Eng

inee

ring

Per

sonn

el

Info

rmat

ion

Sys

tem

s

Sto

res

Rese

arch

&D

evel

opm

ent

Oth

ers

Qua

lity

Fact

ory

prod

uctio

n

Man

ufac

turin

gP

lann

ing

Dept

In n

os

0

25

50

75

100

In %

Pareto

STEP 4 Calculate the cumulative % for individualData No. Of External Phone Calls

7QC Tools

Q7T/PPT- 27

100200100.099.598.597.595.593.591.088.084.079.073.065.555.533.0

Cumulative %

0.51.01.02.02.02.53.04.05.06.07.510.022.533.0

Relative %


Nos.DepartmentSl.No

TRIVIAL MANY

VITAL FEW

Pareto

7QC Tools

Q7T/PPT- 28

10020010073.065.555.533.0

Cumulative %

277.510.022.533.0

Relative %

60Others515Finance420Plant Maintenance345Marketing266Materials1

Nos.DepartmentSl.No

Pareto

7QC Tools

Q7T/PPT- 29

Pareto

66

45

20 15

54

0

30

60

90

120

150

180

Mat

eria

ls

Mar

ketin

g

Pla

nt M

aint

enan

ce

Fina

nce

othe

rs

Dept

In n

os

7QC Tools

Q7T/PPT- 30

66

45

20 15

5433

55.5

65.5

73

100

0

30

60

90

120

150

180

Mat

eria

ls

Mar

ketin

g

Pla

nt M

aint

enan

ce

Fina

nce

othe

rs

Dept

In n

os

0

25

50

75

100

Cum

ulat

ive

%

Pareto

7QC Tools

Q7T/PPT- 31

Pareto

66

45

2015

5433

55.5

65.5

73

100

0

30

60

90

120

150

180

Mat

eria

ls

Mar

ketin

g

Pla

ntM

aint

enan

ce

Fina

nce

othe

rs

Dept

In n

os

0

25

50

75

100

Cum

ulat

ive

%

VitalFew

70 %

7QC Tools

Q7T/PPT- 32

• 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.

Pareto

Why pareto ?

7QC Tools

Q7T/PPT- 33

Add examples from APC………..

7QC Tools

Q7T/PPT- 34

SL# D esc ription O ct '02 Nov '02 D ec '02 Jan '03 Total % D PU C um %1 Sec o n d Pass 520 710 73 759 2062 6 .38 75.972 D efec tive 68 227 22 14 331 1 .02 88. 1 63 B roken C om p 6 48 6 5 65 0 .20 90.564 M is inserted 1 22 1 7 31 0 . 1 0 91 . 705 Skewed C om p 6 14 1 3 24 0 .07 92.586 C om p M issing 15 0 0 4 1 9 0 .06 93.287 O ut of to le ranc e 8 7 0 4 1 9 0 .06 93.988 N o / Low so lder 8 9 0 1 1 8 0 .06 94.649 L ifted 7 2 0 4 1 3 0 .04 95. 1 2

10 Shorts 9 0 0 0 9 0 .03 95 .5Tested 8612 14314 1185 12859 36970P assed 7838 13219 1058 11978 34093 8 .4 8 .02

Q 4' 02 F inal failu re D etails

Q 4 F in a l F a i lu re D eta i ls

2062

331

65 31 24 19 19 18 13 9

75.97

88.16 90.56 91.70 92.58 93.28 93.98 94.64 95.12 95.5

0

500

1000

1500

2000

2500

1 2 3 4 5 6 7 8 9 10Failure

Qty

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00

90.00

100.00

Cum %

Q4 ‘02 Final Failure Details

Data Collection

7QC Tools

Q7T/PPT- 35

You have to cut down your house expenditure by 20% / month

How will you do it ?

Pareto

Same problem, but different approach…

ParetoPareto

7QC Tools

Q7T/PPT- 36

Make a check list of all the expenses in your home & the amount you

spend on these expenses

Pareto

7QC Tools

Q7T/PPT- 37

1300Petrol16

500Insurance Premium13

200Clothes15

300Others17

0Loan repayment14

200Hospital121500Educational11200Travel101500Entertainment & Lifestyle92000Groceries8150Maid servant7300Milkman6120News paper bill5210Cable TV Bill4280Water Bill3500Electricity Bill23000House Rent 1

AmountExpenseSl.No

Pareto

7QC Tools

Q7T/PPT- 38

Arrange these expenses & amounts in an order, with the highest

expense being the first & lowest expense being the last

Pareto

7QC Tools

Q7T/PPT- 39

150Maid servant15

120News paper16

300Others9

12260

0Loan repayment17

200Hospital14200Clothes13200Travel12210Cable TV11280Water bill10

300Milkman8500Insurance premium7500Electricity bill6

1300Petrol51500Educational41500Entertainment32000Groceries23000House rent1

AmountExpenseSl.No

Pareto

7QC Tools

Q7T/PPT- 40

Calculate the percentage contribution of each of these expenses.

Percentage can be calculated by the formula

Individual expense

Total expenseX 100

Pareto

7QC Tools

Q7T/PPT- 41

1.63200Hospital14

1.22150Maid servant15

0.98120Newspaper16

100122600

1.631.631.722.282.452.454.084.0810.6

12.2312.2316.3224.47

Relative %

0Loan repayment17

200Clothes13

200Travel12

210Cable TV11

280Water bill10

300Others9

300Milkman8

500Insurance premium7

500Electricity bill6

1300Petrol5

1500Educational4

1500Entertainment3

2000Groceries2

3000House rent1

Nos.DepartmentSl.No

Pareto

7QC Tools

Q7T/PPT- 42

1000.98120Newspaper16

99.021.22150Maid servant15

97.81.63200Hospital14

10010012260100.0

96.1794.5492.9191.1988.9186.4684.0179.9375.8565.2553.0240.7924.47

Cumulative %

0

1.631.631.722.282.452.454.084.0810.6

12.2312.2316.3224.47

Relative %

0Loan repayment17

200Clothes13

200Travel12

210Cable TV11

280Water bill10

300Others9

300Milkman8



1300Petrol5

1500Educational4

1500Entertainment3

2000Groceries2

3000House rent1

Nos.DepartmentSl.No

Pareto

7QC Tools

Q7T/PPT- 43

1000.98120Newspaper16

99.021.22150Maid servant15

97.81.63200Hospital14

10010012260100.0

96.1794.5492.9191.1988.9186.4684.0179.9375.8565.2553.0240.7924.47

Cumulative %

0

1.631.631.722.282.452.454.084.0810.6

12.2312.2316.3224.47

Relative %

0Loan repayment17

200Clothes13

200Travel12

210Cable TV11

280Water bill10

300Others9

300Milkman8



1300Petrol5

1500Educational4

1500Entertainment3

2000Groceries2

3000House rent1

Nos.DepartmentSl.No

7QC Tools

Q7T/PPT- 44

0

2000

4000

6000

8000

10000

12000

House R

ent

Grocerie

sEnte

rtainm

ent

Educa

tiona

l

Petrol

Others

Expenses

Amou

nt

0102030405060708090100

Cum

ulat

ive

%

7QC Tools

Q7T/PPT- 45

Cause & Effect Cause & Effect diagramdiagram

Cause & effect diagram

7QC Tools

Q7T/PPT- 46

• 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.

Why Cause & Effect ?Cause & effect diagram

7QC Tools

Q7T/PPT- 47

What is Effect ?

EFFECT = A Result or an outcome

EFFECT is What happens


7QC Tools

Q7T/PPT- 48

What is cause ?

CAUSE = Reason or Factor contributing to the EFFECT

CAUSE is WHY it happens


7QC Tools

Q7T/PPT- 49

The analysis of “why?” for “what?”

is cause and effect diagram


7QC Tools

Q7T/PPT- 50

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.


7QC Tools

Q7T/PPT- 51

Pareto chart

Cause-and-effect diagram

Cause & Effect diagram derived from pareto


7QC Tools

Q7T/PPT- 52

Steps of making cause & effect diagram


7QC Tools

Q7T/PPT- 53

Steps of making cause & effect diagramCause & 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 diagramStep 3 • Delete irrelavant causes Step 4• Assign importance factor to the remaining causesStep 5 • Conduct why why analysis if required to find root causes

7QC Tools

Q7T/PPT- 54


Step 1

List all the causes that have been suggested by team members as a part of brain storming.

What is brain storming ?

7QC Tools

Q7T/PPT- 55

Brainstorming is another tool which we use as a part of all the 7 QC tools

7QC Tools

Q7T/PPT- 56

BRAIN STORMING !

Brain storming

7QC Tools

Q7T/PPT- 57

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 - to prevent problem

Brain storming

7QC Tools

Q7T/PPT- 58

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.

Brain storming

7QC Tools

Q7T/PPT- 59

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

Brain storming

7QC Tools

Q7T/PPT- 60

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

Brain storming

7QC Tools

Q7T/PPT- 61

WHY BRAIN STORMING?

TO IDENTIFY THE PROBLEM

TO IDENTIFY CRITICAL CAUSES

TO FIND THE SOLUTION

TO PREVENT THE PROBLEM

Brain storming

7QC Tools

Q7T/PPT- 62

BENEFITS OF BRAIN STORMING?

Brain storming

• Individual is limited in generating ideas and that

group produces more ideas

• Ideas are improved upon by members

• Presence of others increases creativity

• Pooling of ideas and resources is made possible by

coming together as a group

• Individual is limited in generating ideas and that

group produces more ideas

• Ideas are improved upon by members

• Presence of others increases creativity

• Pooling of ideas and resources is made possible by

coming together as a group

7QC Tools

Q7T/PPT- 63


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.

7QC Tools

Q7T/PPT- 64

MATERIALMETHOD

MAN MACHINE

Sub cause

Sub-sub cause

CAUSES EFFECT

PROBLEM

7QC Tools

Q7T/PPT- 65


MACHINEMAN

MATERIAL METHOD

Fatigue

Dimensional Variation

Location

JIGS & FIXTURES

STABILITY

INSPECTION

Method

Attentiveness

SPIRIT

Experience

HEALTH

SKILL

Storage

QUALITY

Inspection

ShapeFORM

Dimension

Feed

WORKING

Spindle speed

Illness Training

ConcentrationInstrument

Clamping

Imbalance

Vibration

SETTING

Degree of tightening

Placement on locator

2

7QC Tools

Q7T/PPT- 66


Step 3

Delete irrelavant causes

7QC Tools

Q7T/PPT- 67


MACHINEMAN

MATERIAL METHOD

Fatigue

Dimensional Variation

Location

JIGS & FIXTURES

STABILITY

INSPECTION

Method

Attentiveness

SPIRIT

Experience

HEALTH

SKILL

Storage

QUALITY

Inspection

ShapeFORM

Dimension

Feed

WORKING

Spindle speed

Illness Training

ConcentrationInstrument

Clamping

Imbalance

Vibration

SETTING

Degree of tightening

Placement on locator

2

The EFFECT or PROBLEM is stated on the right side of the diagramand the major INFLUENCES or CAUSES are listed to the left.

7QC Tools

Q7T/PPT- 68


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.

7QC Tools

Q7T/PPT- 69

Cause Verification

4M Cause Specification Investigation Analysis

Man No focused training Functionwise training

Generic

No method to measure operator's skills

Skill matrix for each workmen

No skill matrix

No OJTPractical training at genba

No 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

7QC Tools

Q7T/PPT- 70


Step 5

Do why why analysis for the significant causes

Atleast ask why 3 times

7QC Tools

Q7T/PPT- 71

Why defects?

D

People

1st Why

Plant

PoliciesProcedure

5th Why

C

3rd Why

4th Why

Thorough investigation of causes

2nd Why


ASK WHY? 5 TIMES

7QC Tools

Q7T/PPT- 72

Examples :- Cylinder does not operate smoothly

Why Answer ActionWhy 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 fluidWhy 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.

Phenomenon(Result)

Cause

Phenomenon(Result)

Cause

Cause

Phenomenon(Result)

Phenomenon(Result)

Primary Secondary

Tertier

‘WHY WHY’ Analysis

7QC Tools

Q7T/PPT- 73

Why Answer ActionDisassemble leaking part.

Why did it leak? Cut in O-ring. Replace O-ring.Why was it cut? Rod has scratch. Remove scratch.

Why was it scratched? Chip was scattered and attached on rod.

Take measure to prevent chips from scattering

Why did chips get attached? Cylinder is located within scattering range of chips. Change cylinder position

Rod cover is not placed. Install cover.Why is rod praced in that Why no cover?

Defective design and installation

Standardize design and installation.

- Oil leaks from cylinder rod each time it operates.

‘WHY WHY’ Analysis

7QC Tools

Q7T/PPT- 74

• 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.


Guidelines

Remember

7QC Tools

Q7T/PPT- 75

MATERIALMETHOD

MAN MACHINE

Sub cause

Sub-sub cause

CAUSES EFFECT

7QC Tools

Q7T/PPT- 76

COPYING PAPERHANDLING

MACHINE PROCESS CONSUMABLES

Party removed

Dust accumulation

POOR QUALITY

OF XEROX COPIES

Paper shortage

Over consumption

Not using specified quality of paper

Non-standard

Non-standard

Supply from various sources

Wrong paper usage

Paper with stablesLack of knowledge

Not understanding the defect codes/ communicating defects

Nominated persons not handling

Paper jam not cleared properly

Untrained personnel handling the machine

Limited machines

Heavy usage

No cleaning

Location

Frequentchanges Serviced by

unauthorized personsImproper service

No periodical service

No stabilizer

Power

High fluctuation

No communication

Specified toner not filled

Lack of knowledge

7QC Tools

Q7T/PPT- 77

Effect

Causes

1


7QC Tools

Q7T/PPT- 78

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.

7QC Tools

Q7T/PPT- 79

Examples from APC………..

7QC Tools

Q7T/PPT- 80

Data Mixed process& Original

MANMAN

METHODMETHOD MATERIALMATERIAL

MACHINEMACHINE

PROCESS PROCESS

SCRAPSCRAP

Scrap Disposal Training/Procedure is inadequate

Machine rejectionsare high.

No process flow

Improper Handling

Handling Pro not defined.

Incoming material.

Improper Storage

Improper /Movement

High Rej in M/C.

Improper StorageIn racks .

No Awareness

Inadequate Training

Improper tools

Program /Nozzleerror

No plan forFeeder maintenance

Identification and SegregationNot done.

No Alarms for M/C Board Jam.

7QC Tools

Q7T/PPT- 81

Data Mixed process& Original

MANMAN

METHODMETHOD MATERIALMATERIAL

MACHINEMACHINE

PROCESS PROCESS

SCRAPSCRAP

Scrap Disposal Training/Procedure is inadequate

Machine rejectionsare high.

No process flow

Improper Handling

Handling Pro not defined.

Incoming material.

Improper Storage

Improper /Movement

High Rej in M/C.

Improper StorageIn racks .

No Awareness

Inadequate Training

Improper tools

Program /Nozzleerror

No plan forFeeder maintenance

Identification and SegregationNot done.

No Alarms for M/C Board Jam.

7QC Tools

Q7T/PPT- 82

LowProductivity

MAN

MATERIAL

METHOD

MACHINE

High Rejection on plastic parts

Scratches

Flow & Black Mark

Printing Defect

Tab & radial BHS problem

GSM error Spindle up

Battery Charging

Operator Skill (Prep of Heat

sink)

Operator absenteeism

Imbalance flow of production

ICT Downtimes and Second pass

High DPU

M/c Cycle time improvement

High Touch up defects before ICT

IC-9 Screening

Serial Number Screening

Board Flow from Wave to ICT

Ishikawa Diagram

7QC Tools

Q7T/PPT- 83

StratificationStratification

Stratification

7QC Tools

Q7T/PPT- 84

Stratification

7QC Tools

Q7T/PPT- 85

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

7QC Tools

Q7T/PPT- 86

Why Stratification?

Stratification

To ascertain the difference between different

categories and to analyse the reasons behind

abnormal distribution.

To obtain clues for identifying the causes

7QC Tools

Q7T/PPT- 87

Case studyProblem : Increased Inventory

sheetsBarsTubesImportsProprietarypressingsFastenersRubberRubberBearings

Shop wiseAssy wiseSub-Assy wiseStage wiseMachine wiseRtRejections

Castings

Raw Material

Components

Work in process

Tubes

Proprietary

Fasteners

Bearings

Shop wise

Sub-Assy wise

TotalInventory

Stratification

7QC Tools

Q7T/PPT- 88

Case study 2

Problem : More No. of Accidents

Stratification

Let us stratify the the data regarding the accidents

7QC Tools

Q7T/PPT- 89

STATISTICSSTATISTICS

REPORTABLE ACCIDENTS REPORTABLE ACCIDENTS :: 08 08

NONNON--REPORTABLE ACCIDENTSREPORTABLE ACCIDENTS :: 3333

NEAR MISS INCIDENTSNEAR MISS INCIDENTS :: 2121

LOST TIME INJURIESLOST TIME INJURIES :: 4141

MANDAYS LOSTMANDAYS LOST : : 187187

Rep.acct.Rep.acct. –– Operator not reporting back to duty Operator not reporting back to duty for for more than 48hrsmore than 48hrs

NonNon--reportable acct.reportable acct. –– Operator disablement extending Operator disablement extending beyond beyond the day of shift but the day of shift but less than 48 hrsless than 48 hrs

Lost time injuryLost time injury –– Reportable + NonReportable + Non--reportablereportable

Stratification

7QC Tools

Q7T/PPT- 90

ANALYSIS ANALYSIS ––REPORTABLE ACCIDENTREPORTABLE ACCIDENT

Total no of reportable accident :Total no of reportable accident : 88

Stratification

7QC Tools

Q7T/PPT- 91

ACCORDING TO CATEGORYACCORDING TO CATEGORY

Temp.workman(3)

38%

Regular Employee (4)

49%

Contract Labour (1)

13%

Total no.of Reportable accidents : Total no.of Reportable accidents : 88

Stratification

7QC Tools

Q7T/PPT- 92

ACCORDING TO PROBLEMACCORDING TO PROBLEM


0

0

0

0

0

0

0

2

6

0 1 2 3 4 5 6 7

wrong assembly

Contact with chemical

Fall from Two wheeler

Fall from Height

others

Hit by objects/Fallen objects

Hit against object

Wrong handling of material handlingequipment

Adjusting/Cleaning/Loading/Unloadingwhile M/C running

No of Accidents

Stratification

7QC Tools

Q7T/PPT- 93


ACCORDING TO BODY PARTS INJUREDACCORDING TO BODY PARTS INJURED

Finger (5)62%

Hand (1)13%

Leg (2)25%

Stratification

7QC Tools

Q7T/PPT- 94

Plant-1 (0)0%

Plant-2 (3)37%

Plant-3 (2)24%

R & D (1)13%

Sp. Wh (1)13%

Others (1)13%

ACCORDING TO PLANTACCORDING TO PLANT


Stratification

7QC Tools

Q7T/PPT- 95


ACCORDING TO UNITACCORDING TO UNIT

1 1 1

0 0 00

1

2

FAB ENG UNIT PAINT VECH UNIT STORES PLATING

No.o

f acc

iden

ts

PLANTPLANT-- 22

Stratification

7QC Tools

Q7T/PPT- 96

ACCORDING TO SHIFTACCORDING TO SHIFT

4

2 2

0 00

1

2

3

4

5

I II III GEN OT

No.o

f acc

iden

ts


Stratification

7QC Tools

Q7T/PPT- 97

ACCORDING TO MONTHACCORDING TO MONTH

0

3

0 0 0 0

2

0

1 1

0

1

0

1

2

3

4

APRIL

MAY

JUNE

JULY

AUGUST

SEPTEM

BER

OCTOBER

NOVEMBER

DECEM

BER

JANUARY

FEBRAUARY

MARCH

No.o

f acc

iden

ts


Stratification

7QC Tools

Q7T/PPT- 98

ACCORDING TO FAULTACCORDING TO FAULT

3

2

3

0

1

2

3

4

OPERATORS FAULT SUPERVISORY FAULT SYSTEM ANDENVIRONMENT FAULT

No.o

f acc

iden

ts


Stratification

7QC Tools

Q7T/PPT- 99

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

Stratification

7QC Tools

Q7T/PPT- 100

Graph & Control charts

Graph&control charts

7QC Tools

Q7T/PPT- 101


GraphWhat is Graph?When there are more than 2 interrelated data sets,you writethe datasets on a graph so as to clearly define therelationships.

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

7QC Tools

Q7T/PPT- 102


Types of Graphs & Its applicationBar graphs,line graphs, pie charts, and band graphs.There are also other specialty graphs such as radarcharts, Z charts and area graphs

Applications

To understand relative sizes of numbers

To understand trends over time

To understand percent-ages of totals

Graph

7QC Tools

Q7T/PPT- 103


Pie chart - Composition of sales turnover 2001-02

Vehicle sales92%

Export Sales1%

Spare parts sales

6%

Other income

1%

Pie charts are used to show percentages or proportions of different components of a specific item.

7QC Tools

Q7T/PPT- 104


Bar chart - Sales performance

1417 19 27

4162

83

104133

162184 194

262

0

50

100

150

200

250

300

90-91 91-92 92-93 93-94 94-95 95-96 96-97 97-98 98-99 99-00 00-01 '01-02 '02-03

Rs Million x 100Plan for 2002-03

Bar charts are used for comparing quantities between persons, regions, time intervals etc.

7QC Tools

Q7T/PPT- 105


Line chart - Hourly output of Workmen

40

45

42 42 42

43

37

38

39

40

41

42

43

44

45

46

Jan Feb Mar Apr May Jun

No.

of w

o rkm

en

Line graphs are used to depict change or variation over time.

7QC Tools

Q7T/PPT- 106


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 Y-axis

• 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.

7QC Tools

Q7T/PPT- 107

To add examples from APC

Histogram

7QC Tools

Q7T/PPT- 108

Productivity improvement

208

277246

278

370397

522

0

100

200

300

400

500

600

OCT NOV DEC JAN FEB MARCH APRILMonth

Uni

ts p

rodu

ced

/ Shi

ft

BeforeAfter

Results

7QC Tools

Q7T/PPT- 109

Results

DPU Trend for Cerror Torre

13.912.1 11.9

8.27.3 7.4

6.5

9.98.3

12

7.4

4.4 4.2 3.8

23.8

20.4

23.9

15.6

11.7 11.610.3

0

5

10

15

20

25

30

% D

PUICTFINALDPU

ICT 13.9 12.1 11.9 8.2 7.3 7.4 6.5FINAL 9.9 8.3 12 7.4 4.4 4.2 3.8DPU 23.8 20.4 23.9 15.6 11.7 11.6 10.3

OCT NOV DEC JAN FEB MAR APRIL

Before

After

7QC Tools

Q7T/PPT- 110

Southern chips Problem trend

April

25%

11%26%

16%

22%ScratchesPrinting missingCkt Brkr BrokenSleeve not putWire interchangeWire not connected

7QC Tools

Q7T/PPT- 111

Histogram

Histogram

7QC Tools

Q7T/PPT- 112

It shows the distribution of data

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.

7QC Tools

Q7T/PPT- 113

• 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.

Histogram

Data

FACTS

7QC Tools

Q7T/PPT- 114

• 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.

Histogram

7QC Tools

Q7T/PPT- 115

• 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

Histogram

7QC Tools

Q7T/PPT- 116

• 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.

Histogram

7QC Tools

Q7T/PPT- 117

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.

Histogram

What is histogram ?

7QC Tools

Q7T/PPT- 118

How to make a histogram?Let us make a histogram using an example.

Histogram

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.

7QC Tools

Q7T/PPT- 119

SampleNumber1 - 10 2.51 2.517 2.522 2.522 2.51 2.511 2.519 2.532 2.543 2.52511 - 20 2.527 2.536 2.506 2.541 2.512 2.515 2.521 2.536 2.529 2.52421 - 30 2.529 2.523 2.523 2.523 2.519 2.528 2.543 2.538 2.518 2.53431 - 40 2.52 2.514 2.512 2.534 2.526 2.53 2.532 2.526 2.523 2.5241 - 50 2.535 2.523 2.526 2.525 2.532 2.522 2.502 2.53 2.522 2.51451 - 60 2.533 2.51 2.542 2.524 2.53 2.521 2.522 2.535 2.54 2.52861 - 70 2.525 2.515 2.52 2.519 2.526 2.527 2.522 2.542 2.54 2.52871 - 80 2.531 2.545 2.524 2.522 2.52 2.519 2.519 2.529 2.522 2.51381 - 90 2.518 2.527 2.511 2.519 2.531 2.527 2.529 2.528 2.519 2.521

Results of Measurement

Diameter after grinding

Histogram

7QC Tools

Q7T/PPT- 120

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

7QC Tools

Q7T/PPT- 121

STEP 1 Collect data

CASE STUDYPeriod : wk no. 15 to 20Material : ms flange collarUOM : mmThickness : 9 mm + 1.5 mm

9.9 9.3 10.2 9.4 10.1 9.6 10.1 9.9 9.89.8 9.8 10.1 9.9 9.7 9.8 10.0 9.9 9.69.7 9.4 9.6 10.0 9.8 9.9 10.4 10.1 10.010.2 10.1 9.8 10.1 10.3 10.0 9.8 10.2 10.79.9 10.7 9.3 10.3 9.9 9.8 9.5 9.8 9.49.3 10.2 9.2 9.9 9.7 9.9 9.5 9.8 9.49.0 9.5 9.7 9.7 9.8 9.8 9.6 9.3 9.710.0 9.7 9.4 9.8 9.4 9.6 10.3 10.0 9.89.5 9.7 10.6 9.5 10.1 10.0 10.1 9.8 9.39.6 9.4 10.1 9.5 10.1 10.2 9.5 9.8 9.310.3 9.6 9.7 9.7 10.1 9.8 10.0 9.7 10.09.5 9.5 9.8 9.9 9.2 10.0 9.7 10.0 9.79.9 10.4 9.3 9.6 10.2 9.7 9.7 9.7 10.79.9 10.2 9.8 9.3 9.6 9.5 10.7 9.6

N = 125

7QC Tools

Q7T/PPT- 122

CASE STUDY

STEP 2 DETERMINE THRE LARGEST AND SMALLEST VALUEMinimum Maximum

9.9 9.3 10.2 9.4 10.1 9.6 10.1 9.9 9.8 9.3 10.29.8 9.8 10.1 9.9 9.7 9.8 10.0 9.9 9.6 9.6 10.19.7 9.4 9.6 10.0 9.8 9.9 10.4 10.1 10.0 9.4 10.410.2 10.1 9.8 10.1 10.3 10.0 9.8 10.2 10.7 9.8 10.79.9 10.7 9.3 10.3 9.9 9.8 9.5 9.8 9.4 9.3 10.79.3 10.2 9.2 9.9 9.7 9.9 9.5 9.8 9.4 9.2 10.29.0 9.5 9.7 9.7 9.8 9.8 9.6 9.3 9.7 9.0 9.810.0 9.7 9.4 9.8 9.4 9.6 10.3 10.0 9.8 9.4 10.39.5 9.7 10.6 9.5 10.1 10.0 10.1 9.8 9.3 9.5 10.69.6 9.4 10.1 9.5 10.1 10.2 9.5 9.8 9.3 9.3 10.210.3 9.6 9.7 9.7 10.1 9.8 10.0 9.7 10.0 9.6 10.39.5 9.5 9.8 9.9 9.2 10.0 9.7 10.0 9.7 9.2 10.09.9 10.4 9.3 9.6 10.2 9.7 9.7 9.7 10.7 9.3 10.79.9 10.2 9.8 9.3 9.6 9.5 10.7 9.6 9.3 10.7

9.0 10.7

N = 125

7QC Tools

Q7T/PPT- 123

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 - 1

No.of data points No. of classes

Under 50 5 – 7

50 – 100 6 – 10

100 – 250 7 – 12

Over 250 10 - 20

Method – 2No. Of Classes – K =√N where,

N = No. Of sample

For example, if N = 125K =√125 = 11

Let us use K = 10 classes

7QC Tools

Q7T/PPT- 124

CASE STUDY

STEP 3 Obtain the range of R

Maximum value – Minimum Value = R

10.7 – 9.0 = 1.7

R = 1.7

7QC Tools

Q7T/PPT- 125

CASE STUDY

STEP 5 Determine the class width ‘H’

R (Range)= H

K (# of classes)1.7

= 0.1710

Can be rounded off to 0.20

7QC Tools

Q7T/PPT- 126

CASE STUDY

STEP 6 Divide the value of class boundaryFor 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.

7QC Tools

Q7T/PPT- 127

CASE STUDY

STEP 7 Construct a frequency table

Class #

Class Boundaries Midpoint 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

Q7T/PPT- 128

CASE STUDY

STEP 8 Construct Histogram

05

101520253035

8.95 9.15 9.35 9.55 9.75 9.95 10.15 10.35 10.55 10.75Thickness in mm

Freq

uenc

y USL

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.

7QC Tools

Q7T/PPT- 129

HISTOGRAM

Having two peaks

Having a cut end

Having extraordinarily high value in

the end internal

Having an isolated peak

Right & Left symmetrical

Slopping the right

Slopping to the left

7QC Tools

Q7T/PPT- 130

Average response time to patient rings (1st shift)

050

100150200

1 2 3 4 5 6 7 8 9 1Minutes

# O

f Res

pons

es

Histogram - Daily Example Height of 100 men

010203040

63 65 67 69 71Height (inches)

# O

f Men

Histogram-ManufacturingPrint Density

02468

0.6 0.8 0.1 1.2 1.4Block density of print

Freq

uenc

y

Histogram – Administration/Service Example

7QC Tools

Q7T/PPT- 131

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

Histogram

Application

7QC Tools

Q7T/PPT- 132

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.

Histogram

Uses of Histogram

7QC Tools

Q7T/PPT- 133

Scatter diagramScatter diagram

Scatter diagram

7QC Tools

Q7T/PPT- 134

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?

Scatter diagram Scatter diagram

7QC Tools

Q7T/PPT- 135

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.

Scatter diagram

7QC Tools

Q7T/PPT- 136

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

Scatter diagram

7QC Tools

Q7T/PPT- 137

Examples of such relationships

Speed Vs Mileage

Cutting speed Vs Tool life

Etc……

Scatter diagram

7QC Tools

Q7T/PPT- 138

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.

Scatter diagram

7QC Tools

Q7T/PPT- 139

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.

=

Scatter diagram

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.

7QC Tools

Q7T/PPT- 140

Step 3Plot the data on the section paper. Step 4Enter 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 diagramb) Time intervalc) Number of pairs of datad) Title & units of each axise) Name (etc) of the person who made the diagram

Scatter diagram

7QC Tools

Q7T/PPT- 141

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.

Scatter diagram

7QC Tools

Q7T/PPT- 142

Date Air pressure Percent(kgf/cm2) Defective

Oct-01 8.6 0.8892 8.9 0.8843 8.8 0.8744 8.8 0.8915 8.4 0.8746 8.7 0.8867 9.2 0.9118 8.6 0.9129 9.2 0.89510 8.7 0.89611 8.4 0.89412 8.2 0.86413 9.2 0.92214 8.7 0.90915 9.4 0.90516 8.7 0.89217 8.5 0.87718 9.2 0.88519 8.5 0.86620 8.3 0.89621 8.7 0.89622 9.3 0.92823 8.9 0.88624 8.9 0.90825 8.3 0.88126 8.7 0.88227 8.9 0.90428 8.7 0.91229 9.1 0.92530 8.7 0.872

Data of blowing air pressure & percent defective of plastic tank

Scatter diagram

7QC Tools

Q7T/PPT- 143

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 (%)

Scatter diagram

7QC Tools

Q7T/PPT- 144

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.

Scatter diagram

7QC Tools

Q7T/PPT- 145

0.85

0.86

0.87

0.88

0.89

0.9

0.91

0.92

0.93

8 8.5 9 9.5

Scatter diagram

7QC Tools

Q7T/PPT- 146

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).

0.85

0.86

0.87

0.88

0.89

0.9

0.91

0.92

0.93

8 8.5 9 9.5

(Oct 1 – Oct 30)

n=30

P er c

e nta

ge d

e fe c

ti ve

Blowing air pressure

Scatter diagram

7QC Tools

Q7T/PPT- 147

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

Scatter diagram

7QC Tools

Q7T/PPT- 148

05

101520253035

0 5 10 15 20

Series1

Positive correlation

Scatter diagram

If y increases with x or the vice versa,then x and y are positively correlated.

7QC Tools

Q7T/PPT- 149

050

100150200250300350

0 100 200 300 400

Series1

Negative correlation

Scatter diagram

If y decreases as x increases, then the two

types of data are negatively correlated.

7QC Tools

Q7T/PPT- 150

0100200300400500600700

0 100 200 300 400

Series1

No correlation

Scatter diagram

If no significant relationship is apparent between x and y, then the two data types are not correlated.

7QC Tools

Q7T/PPT- 151

0

10

20

30

40

0 5 10 15 20

Series1

0

100

200

300

400

500

0 100 200 300 400

Series1

Positive correlation may be present Negative correlation may be present

Scatter diagram

7QC Tools

Q7T/PPT- 152

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?

Scatter diagram

7QC Tools

Q7T/PPT- 153

Try a scatter diagram !

No. of hours of study/day0.5 1.0 1.5 2.0 2.5

Perc

enta

ge o

f mar

ks50

60

70

80

90

Scatter diagram

7QC Tools

Q7T/PPT- 154

Documents

7qc Tools Test