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

Using the relation (x_i) = 
\(\frac{(upper\, class\, limit \,+\, lower\, class\, limit)}{2}\)

And, class size of this data = 3

Let the assumed mean (A) = 75.5

So, let’s calculate d_i, u_i, f_iu_i as following:

From table, it’s seen that

N = 30 and h = 3

So, the mean = A + h x (\(\frac{Σf_i u_i}{N}\))

= 75.5 + 3 x (\(\frac{4}{30}\))

= 75.5 + \(\frac{2}{5}\)

= 75.9

Therefore, the mean heart beats per minute for those women are 75.9 beats per minute.