Let M denote the median of the following frequency distribution
Class
0 - 4
4 - 8
8 - 12
12 - 16
16 - 20
Frequency
3
9
10
8
6
Then 20M is equal to :
Solutions · 1
Official solution
Total frequency N=3+9+10+8+6=36, so N/2=18.
Cumulative frequencies: 0--4: 3; 4--8: 12; 8--12: 22; ... Median class is 8--12 (cf. just before =12, class frequency =10).
\[M = L+\frac{N/2-CF}{f}\times h = 8+\frac{18-12}{10}\times4 = 8+2.4 = 10.4\]
\[20M = 20\times10.4 = 208\]