Question

Example 35. Calculate standard deviation by the actual mean method:
40-50
30-40
20-30
10-20
0-10
Marks
2
5
6
3
4
No. of students
​

Answer 1

Explanation:

ANSWER

Class inreval

Mid values (x

i

)

Frequency (f

i

)

d

i

=x

i

−A

u

i

=

h

d

i

F

i

u

i

0-10

5

4

-20

-2

-8

10-20

15

6

-10

-1

-6

20-30

25=A

10

0

0

0

30-40

35

20

10

1

20

40-50

45

10

20

2

20

N=50

Total=26

h=10,A=25,N=50,∑f

i

u

i

=26

Mean (

x

)=A+h[

N

1

example

∑f

i

u

i

]

put the values

Mean=30.2

Answer 2

Answer:

27

Explanation:

profit per shop

40-50

30-40

20-30

10-20

0-10

mid value(x)

45

35

25

15

5

marks(f)

2

5

6

3

4

deviation dx=x-25

+20

+10

0

-10

-20

standard deviation i =10(ds)

2

1

0

-1

-2

mean=25+4_10

20×

25+40_

20

25+2

=27