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
Number of women
65-68
2
68-71
4
71-74
3
74-77
8
77-80
7
80-83
4
83-86
2

75.92

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35.92

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60.92

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80.92

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Solution

The correct option is A 75.92

No. heart beats per min
(Class Interval) ( $f_{i}$ ) no. of women
$x_{i}$ $x_{i} f_{i}$

65-68 2 66. 5 133

68-71 4 69.5 278

71-74 3 72.5 217.5

74-77 8 75.5 604

77-80 7 78.5 549.5

80-83 4 81.5 326

83-86 2 84.5 169

Total 30 2277
$M e a n h e a r t b e a t s = \frac{\sum f_{i} x_{i}}{\sum f_{i}} = \frac{2277}{30} = 75.92$

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Similar questions

Q. 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.

Number of heart beats per minute:	65-58	68-71	71-74	74-77	77-80	80-83	83-86
Number of women:	2	4	3	8	7	4	2

Q. 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	$65 - 68$	$68 - 71$	$71 - 74$	$74 - 77$	$77 - 8$ 0	$80 - 83$	$83 - 86$
Number of women	$2$	$4$	$3$	$8$	$7$	$4$	$2$

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

$\begin{matrix} Number of heart beats per minute & 68 - 71 & 71 - 74 & 74 - 77 & 77 - 80 & 80 - 83 & 83 - 86 Number of Women & 2 & 4 & 3 & 8 & 7 & 4 & 2 \end{matrix}$

Question 4
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.

$\begin{matrix} Number of heart beats per minute & 65 - 68 & 68 - 71 & 71 - 74 & 74 - 77 & 77 - 80 & 80 - 83 & 83 - 86 Number of women & 2 & 4 & 3 & 8 & 7 & 4 & 2 \end{matrix}$

Q. The number of heart beats per minute is known as _______ .

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Number of heart beats per minute	Number of women
65-68	2
68-71	4
71-74	3
74-77	8
77-80	7
80-83	4
83-86	2

No. heart beats per min (Class Interval) ( $f_{i}$ )	no. of women	$x_{i}$	$x_{i} f_{i}$
65-68	2	66. 5	133
68-71	4	69.5	278
71-74	3	72.5	217.5
74-77	8	75.5	604
77-80	7	78.5	549.5
80-83	4	81.5	326
83-86	2	84.5	169
Total	30		2277

The correct option is A 75.92No. heart beats per min (Class Interval) (fi)no. of women xi xifi 65-68 2 66. 5 133 68-71 4 69.5 278 71-74 3 72.5 217.5 74-77 8 75.5 604 77-80 7 78.5 549.5 80-83 4 81.5 326 83-86 2 84.5 169 Total 30 2277 Mean heart beats=∑fixi∑fi=227730=75.92