# Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarised 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 | 77-78 | 80-83 | 83-86 |

Number of women: | 2 | 4 | 3 | 8 | 7 | 4 | 2 |

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Given:

Thirty women were examined in a hospital by a doctor and the number of heartbeats per minute was recorded.

To do:

We have to find the mean heartbeats per minute for the women.

Solution:

Let the assumed mean be $A=75.5$

We know that, Mean $=A+h \times \frac{\sum{f_iu_i}}{\sum{f_i}}$

Therefore,

Mean $=75.5+3\times\frac{4}{30}$

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

$=75.5+0.4$

$=75.9$

The mean heartbeats per minute for the women is $75.9$.

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