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.

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?

• A. $8.2$ plants
• B. $6.5$ plants
• C. $5.7$ plants
• D. None of these

Answer 1

Answer: (D)

None of these

Answer: Using direct method to calculate mean :

No. of plants	No. of houses	$x_i$	$f_i.x_i$
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
	$\Sigma f_i=20$		$\Sigma f_i.x_i=162$

Mean=$\frac{\Sigma f_i.x_i}{\Sigma f_i}=\frac{162}{20}=8.1plants$

We used direct method for finding the mean as the width of the class is very small and also the frequency for each class have very small values. Thus, it will be easy to calculate.