solution:
From the given information, let us expect the mean as A = 75.5
Class size (h) = 3
Presently, find the ui and fiui as follows:
Class Interval Number of ladies (fi) Mid-point (xi)
fiui
65-68 2 66.5 -3 -6
68-71 4 69.5 -2 -8
71-74 3 72.5 -1 -3
74-77 8 75.5 0 0
77-80 7 78.5 1 7
80-83 4 81.5 3 8
83-86 2 84.5 3 6
Aggregate fi= 30 Sum fiui = 4
= 75.5 + 3×(4/30)
= 75.5 + 4/10
= 75.5 + 0.4
= 75.9
Thusly, the mean heart beats each moment for these ladies is 75.9