Question

If the mean of the following frequency distribution is 7.2, find value of ‘k’.

x	2	4	6	8	10	12
f	4	7	10	16	k	3

Answer 1

Σf_i = 40 + k; 

Σf_i x_i = 260 + 10k

Given that \(\overline x\) = 7.2

But \(\overline x\) = \(\frac {\sum f_1x_i}{\sum f_i}\)

7.2 = \(\frac {260 + 10k}{40 + k}\)

288.0 + 7.2k = 260 + 10k

10k – 7.2k = 288 – 260 

2.8k = 28

k = 28/2.8 = 10