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Question -

A survey was conducted by a group of students as a part of their environment awareness programme, in which they collected the following data regarding the number of plants in 20 houses in a locality. Find the mean number of plants per house.



Answer -

Number of Plants

0-2

2-4

4-6

6-8

8-10

10-12

12-14

Number of Houses

1

2

1

5

6

2

3
Which method did you use for finding the mean,and why?

Solution:

In order to find themean value, we will use direct method because the numerical value of fi and xi are small.

Find the midpoint ofthe given interval using the formula.

Midpoint (xi) = (upper limit + lower limit)/2

No. of plants

(Class interval)

No. of houses

Frequency (fi)

Mid-point (xi)

fixi

0-2

1

1

1

2-4

2

3

6

4-6

1

5

5

6-8

5

7

35

8-10

6

9

54

10-12

2

11

22

12-14

3

13

39

Sum fi = 20

Sum fixi = 162

The formula to findthe mean is:

Mean = x̄ = ∑fi xi /∑fi 

= 162/20

= 8.1

Therefore, the mean number of plants per house is 8.1

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