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# Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarized as follows - CBSE Class 10 - Mathematics

#### Question

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

#### Solution

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

x_i  = ("Upper class limit + Lower class limit")/2

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 ui = di/3 fiui 65 − 68 2 66.5 − 9 -3 -6 68 − 71 4 69.5 − 6 -2 -8 71 − 74 3 72.5 − 3 -1 -3 74 − 77 8 75.5 0 0 0 77 − 80 7 78.5 3 1 7 80 − 83 4 81.5 6 2 8 83 − 86 2 84.5 9 3 6 Total 30 4

From the table, we obtain

sumf_i = 30

sumf_iu_i = 4

mean barx=a+((sumf_iu_i)/(sumf_i))xxh

= 75.5 +(4/30) xx 3

= 75.5 + 0.4 = 75.9

Therefore, mean hear beats per minute for these women are 75.9 beats per minute.

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#### APPEARS IN

NCERT Solution for Mathematics Textbook for Class 10 (2019 to Current)
Chapter 14: Statistics
Ex. 14.10 | Q: 4 | Page no. 271

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Solution Thirty women were examined in a hospital by a doctor and the number of heart beats per minute were recorded and summarized as follows Concept: Mean of Grouped Data.
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