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 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

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Detailed Solution

From the given data, let us assume the mean as A = 75.5

x_i= $\frac{u p p e r l i m i t + l o w e r l i m i t}{2}$

Class size (h) = 3

Now, find the u_iand f_iu_i as follows:

Mean = x̄ = A + h $\frac{\sum_{} f_{i} u_{i}}{\sum_{} f_{i}}$

= 75.5 + 3× $\frac{4}{30}$

= 75.5 + $\frac{4}{10}$

= 75.5 + 0.4

= 75.9

Therefore, the mean heart beats per minute for these women is 75.9.

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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