Calculate mean deviation about median for following readings
Class20−4040−6060−8080−100Fi20443040
18.8
We need to calculate the median first.
Class20−4040−6060−8080−100fi20443040c.fi206494134
Median=l+N2−cfX h
Median class=(60−80) class as it contains (1342)th term
∴l=60,N=134,f=30,h=20.
∴ Median =60+(1342−6430) 20
=60+(67−6430)20=60+2=62
∴M=62
Class20−4040−6060−8080−100fi20443040Meandeviations|30−62||50−62||70−62||90−62|=32=12=8=28
Mean deviation about median (M) =4∑i−1∑4i=1fi|xi−M|∑40−1fi
=20(32)+44(12)+30(8)+40(28)134
=640+528+240+1120134
=2528134=18.8