Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarized as follows. Find the mean heart beats per minute for these women, choosing a suitable method.
Number of heart beats per minute65−6868−7171−7474−7777−8080−8383−86Number of women2438742
We may find the class mark of each interval (xi) by using the relation:
xi =Upper class limit + lower class limit2
Class size h of this data = 3
Now, taking 75.5 as assumed mean a; we may calculate di,ui,fiui as following:
Number of heart beats per minuteNumber of women fixidi=xi−75.5ui=xi−75.5hfiui65−68266.5−9−3−668−71469.5−6−2−871−74372.5−3−1−374−77875.500077−80778.531780−83481.562883−86284.5936Total30 4
Now, we may observe from the table that:
So, mean heart beats per minute for these women are 75.9 beats per minute.