Question

Thirty women were examined in a hospital by a doctor and the number of heart beats per minute recorded and summarized as follows. Find the mean heart beats per minute for these women, choosing a suitable method.
Number of
heart beats
per minute: 65-68 68-71 71-74 74-77 77-80 80-83 83-86

Number of
women: 2 4 3 8 7 4 2

Answer 1

The mean heart beats per minute for these women is 75.9

I have attached the table of calculations in the image section.

Consider the figure while going through the following calculations.

∑ fi = 30

∑ fi * ui = 4

Mean = a + h × (∑ fi * ui ) / (∑ fi )

a = assumed mean = 75.5

h = class interval = 68 - 65 = 3

Mean = 75.5 + 3 × (4 / 30)

= 75.5 + 1 × (4 / 10)

= 75.5 +  (2 / 5)

= 75.9

Therefore, the mean heart beats per minute of women are 75.9