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

Thirty women were examined in a hospital by a doctor and the number of heart beats per minute recorded and summarised as follows. Find the mean heat beats per minute for these women, choosing a suitable method.

Solution:

Let the assumed mean be A = 75.5 and h = 3.

We know that mean, $\bar{X}=A+h\left(\frac{1}{N} \sum f_{i} u_{i}\right)$

Now, we have $N=\sum f_{i}=30, \sum f_{i} u_{i}=4, h=3$ and $A=75.5$.

Putting the values in the above formula, we have

$\bar{X}=A+h\left(\frac{1}{N} \sum f_{i} u_{i}\right)$

$=75.5+3\left(\frac{1}{30} \times(4)\right)$

$=75.5+\frac{12}{30}$

$=75.5+0.4$

$=75.9$

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