1.   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.


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



Solution:


Number of plants
0-2
2-4
4-6
6-8
8-10
10-12
12-14
Total
Number of houses($f_i$)
1
2
1
5
6
2
3
20
MidPoint($x_i$)
1
3
5
7
9
11
13
$f_ix_i$
1
6
5
35
54
22
39
162


$x̄$ = ${∑f_ix_i}/{∑f_i}$ =$162/20$
$x̄$ = $8.1$


2.Consider the following distribution of daily wages of 50 workers of a factory.


Daily wages (in `)
Number of workers 
500-520
12
520-540
14
540-560
8
560-580
6
580-600
10

Find the mean daily wages of the workers of the factory by using an appropriate method.

Solution:
Let use assumed mean method .
Let the assume mean be 550. Therefore $a$ =550

Daily wages (in ₹)
Number of workers ($f_i$) 
Midpoint($x_i$)
$d_i=x_i-a$
$f_id_i$
500-520
12
510
-40
-480
520-540
14
530
-20
-280
540-560
8
550
0
0
560-580
6
570
20
120
580-600
10
590
40
400
Total
50
-240


Mean = $x̄$ =   $a$ +${Σf_i d_i }/{Σf_i}$ =$550 + (-240)/50$
				 = $550 - 4.8$
				 = $545.2$
				 
	Therefore mean daily wages of workers = $545.2$