6

Correlation Analysis

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ccorrelation is your life . without relation no correlation exists .....

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Page

7 o

f 11

Exa

mpl

e: C

alcu

late

the

coef

ficie

nt o

f cor

rela

tion

and

inte

rpre

t its

val

ue.

Sale

s R

even

ue

Adv

ertis

ing

Expe

nditu

re

5-10

10

-15

15-2

0 20

-25

75-1

25

4 1

- -

125-

175

7 6

2 1

175-

225

1 3

4 2

225-

275

1 1

3 4

AN

S: r

= 0.

596

Exa

mpl

e: C

alcu

late

the

coef

ficie

nt o

f cor

rela

tion

and

inte

rpre

t its

val

ue.

Age

Gro

up

Sum

Ass

ured

10

,000

20

,000

30

,000

40

,000

50

,000

20

-30

4 6

3 7

1 30

-40

2 8

15

7 1

40-5

0 3

9 12

6

2 50

-60

8 4

2 -

- A

NS:

r =

-0.2

56

Exa

mpl

e:

expe

nses

from

the

data

giv

en b

elow

and

inte

rpre

t its

valu

e:

Adv

ertis

ing

Expe

nses

(Lak

hs)

10

12

15

23

20

Sale

s (La

khs)

14

17

23

25

21

AN

S: r

= +0

.865

Exa

mpl

e: S

how

that

the

coef

ficie

nt o

f cor

rela

tion

lies b

etw

een

-1 a

nd +

1.

Ans

:

Let

a

nd

Now

i.e.

Page

8 o

f 11

Sim

ilarly

usin

g w

e ge

t

Whi

ch c

oncl

udes

Prob

able

Err

or:

The

prob

able

err

or o

f the

coe

ffici

ent o

f cor

rela

tion

is o

btai

ned

as

The

coef

ficie

nt o

f cor

rela

tion

in th

e po

pula

tion

expe

cted

to b

e

Cor

rela

tion

Coe

ffic

ient

Ran

k co

rrel

atio

n m

etho

d is

appl

ied

whe

n th

e ra

nk o

rder

dat

a ar

e av

aila

ble

or

whe

n ea

ch v

aria

ble

can

be r

anke

d in

som

e or

der.

The

mea

sure

bas

ed o

n th

is

met

hod

is kn

own

as ra

nk c

orre

latio

n co

effic

ient

. Thi

s m

etho

d is

appl

ied

to th

e si

tuat

ion

in w

hich

exa

ct n

umer

ical

mea

sure

men

t are

not

ava

ilabl

e. F

or in

stan

ce,

sinc

erity

or

ho

nesty

of

ea

ch

empl

oyee

. C

oeff

icie

nt d

enot

ed b

y a

nd d

efin

ed a

s

D re

fers

to th

e di

ffere

nce

of ra

nks b

etw

een

paire

d ite

ms i

n tw

o se

ries.

[Pro

of: s

ee N

urul

Isla

m P

age

272]

Exa

mpl

e: T

wo

man

ager

s ar

e as

ked

to r

anke

d a

grou

p of

em

ploy

ee in

ord

er o

f po

tent

ial f

or e

vent

ually

bec

omin

g to

p m

anag

ers.

The

rank

ings

are

as f

ollo

ws:

Empl

oyee

A

B

C

D

E

F G

H

I

J

Ran

king

by

Man

ager

1

10

2 1

4 3

6 5

8 7

9

Ran

king

by

Man

ager

2

9 4

2 3

1 5

6 8

7 10

Com

pute

the

coef

ficie

nt o

f ran

k co

rrel

atio

n an

d co

mm

ent o

n th

e va

lue.

Page

9 o

f 11

Solu

tion:

Em

ploy

ee

A

10

9

1 B

2 4

4 C

1 2

1 D

4

3 1

E 3

1 4

F 6

5 1

G

5 6

1 H

8

8 0

I 7

7 0

J 9

10

1 N

=10

=14

Thus

we

find

that

the

re i

s a

high

deg

ree

of p

ositi

ve c

orre

latio

n in

the

ran

ks

assig

ned

by th

e tw

o m

anag

ers.

Exa

mpl

e: C

ompu

te th

e ra

nk c

orre

latio

n co

effic

ient

for t

he fo

llow

ing

data

od

2 te

sts g

iven

to c

andi

date

s for

a c

ritic

al jo

b an

d co

mm

ent o

n th

e va

lue.

Prel

imin

ary

test

92

89

87

86

83

77

71

63

53

50

Fina

l tes

t 86

83

91

77

68

85

52

82

37

57

Solu

tion:

Pr

elim

inar

y te

st

Fina

l tes

t

92

10

86

9 1

89

9 83

7

4 87

8

91

10

4 86

7

77

5 4

83

6 68

4

4 77

5

85

8 9

71

4 52

2

4 63

3

82

6 9

53

2 37

1

1 50

1

57

3 4

N=1

0

=44

Page

10

of 1

1

Thus

we

find

that

the

re i

s a

high

deg

ree

of p

ositi

ve c

orre

latio

n be

twee

n pr

elim

inar

y te

st an

d fin

al te

st

Tie

in R

anks

:

An

adju

stmen

t of t

he a

bove

form

ula

is m

ade

whe

n ra

nks a

re e

qual

Exa

mpl

e: A

n ex

amin

atio

n of

eig

ht a

pplic

ants

for

a po

st w

as ta

ken

by a

firm

. Fr

om t

he m

arks

obt

aine

d th

e ap

plic

ants

in

the

Bang

la a

nd E

nglis

h pa

pers

, C

ompu

te th

e ra

nk c

orre

latio

n co

effic

ient

:

App

lican

t A

B

C

D

E

F G

H

Mar

ks in

Ban

gla

15

20

28

12

40

60

20

80

Mar

ks in

Eng

lish

40

30

50

30

20

10

30

60

Solu

tion:

Mar

ks in

Ban

gla

Fi

nal t

est

15

2 40

6

16

20

3.5

30

4 0.

25

28

5 50

7

4 12

1

30

4 9

40

6 20

2

16

60

7 10

1

36

20

3.5

30

4 0.

25

80

8 60

8

0 N

=8

=8

1.5

Page

11

of 1

1 M

arks

20

is re

peat

ed 2

tim

es, h

ence

a

nd M

arks

30

is re

peat

ed 3

tim

es,

henc

e .