Question

The following table gives the number of children of 150 families in a village

No. of children (x):	0	1	2	3	4	5
No. of families (f):	10	21	55	42	15	7

Find the average number of children per family.

Answer 1

Let the assumed mean (A) = 2

No. of children (xi)	No. of families (fi)	ui = xi - A = xi - 2	fiui
0	10	-2	-20
1	21	-1	-21
2	55	0	0
3	42	1	42
4	15	2	30
5	7	3	21
	N = 150		\(\sum\)fiui = 52

Average number of children per family = A + \(\frac{\sum f_i u_i}{N}\)

\(=2+\frac{52}{150}=\frac{300+52}{150}\)

\(=2.35\) (approx)