Thirty women were examined in a hospital by a doctor and the number of

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 - 6868 - 7171 - 7474 - 7777 - 8080 - 8383 - 86 Number of women:2438742

Answer»

We may find class mark of each interval (xi) by using the relation.

x_i \(=\frac{Upper\,class\,limit+Lower\,class\, limit}{2}\)

Class size of this data = 3

Now taking 75.5 as assumed mean (A), we may calculate d_i, u_i, f_iu_i as following:

Now we may observe from table that ∑f_i= 30, ∑f_iu_i = 4

Mean (X̅) = di + \(\frac{\sum f_ iu_i }{\sum f_i}\times h\)

\(=75.5\,+\frac{4}{30}\times3\)

\(=75.5 \,+0.4 = 75.9\)