We may find class mark of each interval (xi) by using the relation.
Class size of this data = 3
Now taking 75.5 as assumed mean (A), we may calculate di, ui, fiui as following:
Now we may observe from table that ∑fi = 30, ∑fiui = 4
Mean (X̅) = di + * h
= 75.5 + * 3
= 75.5 + 0.4 = 75.9
So mean of heart beat per minute of women are 75.9 beats per minute.
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