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In this page 10th grade statistics solution4 we are going to see
solution of some practice questions of 10th grade statistics worksheet1.

Question 10 :

The time (in seconds) taken by a group of people to walk across a pedestrian crossing is given in the table below.

Time (in sec) 5-10 10-15 15-20 20-25 25-30

No of people 4 8 15 12 11

Calculate the standard deviation

Solution:

here we have to consider the first data that is time as (x) and no of people as (f). Since the time is in the form of interval we have to find the mid value and take it as x.

x

f

d = x-17.5

d²

fd²

7.5

4

7.5-17.5=10

100

400

12.5

8

12.5-17.5=-5

25

200

17.5

15

17.5-17.5=0

0

0

22.5

12

22.5-17.5=5

25

300

27.5

11

27.5-17.5=10

100

1100

Σ f = 50

Σfd²=2000

σ = √(Σfd²/Σf)

= √(2000/50)

= √40

= 6.32

Question 11 :

A group of 45 house owners contributed money towards green
environment of their street. The amount of money collected is shown in
the table below.

Amount 0-20 20-40 40-60 60-80 80-100

No of house 2 7 12 19 5

Calculate the standard deviation

Solution:

here we have to consider the first data that
is amount as (x) and no of horse as (f). Since the amount is in the form of
interval we have to find the mid value and take it as x.