We can see in series-II the highest frequency range is 40−50. Estimated Mode =L+
fm−fm1
(fm−fm−1)+(fm−fm+1)
×w where: Lis the lower class boundary of the modal group fm−1 is the frequency of the group before the modal group fm is the frequency of the modal group ⋅fm+1 is the frequency of the group after the modal group w is the group width L=40,fm−1=4,fm=58,fn+1=26,W=10 mode =40+