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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. Fine 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

Answer:

To find the class mark of each interval (xi), the following relation is used.

Class size, h, of this data = 3

Taking 75.5 as assumed mean (a), di, ui, fiui are calculated as follows.

Number of heart beats per minute

Number of women

fi

xi

di = xi − 75.5

fiui

...

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