Question

Find the mean of the distribution:

Class	1 – 3	3 – 5	5 – 7	7 – 10
Frequency	9	22	27	17

Answer 1

We first, find the class mark x_i of each class and then proceed as follows.

Class	Class marks `(bb(x_i))`	Frequency `(bb(f_i))`	`bb(f_ix_i)`
1 – 3	2	9	18
3 – 5	4	22	88
5 – 7	6	27	162
7 – 10	8.5	17	144.5
		`sumf_i = 75`	`sumf_ix_i = 412.5`

Therefore, mean `(barx) = (sumf_ix_i)/(sumf_i)`

= `412.5/75`

= 5.5

Hence, mean of the given distribution is 5.5.