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

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

          

Answers (2)

best_answer

Let  a = 75.5

 

No. of heartbeats

per minute   

Number of

women f_i

Class mark

x_i

 d_i = x_i -a f_id_i
65-68 2 66.5 -9 -18
68-71 4 69.5 -6 -24
71-74 3 72.5 -3 -9
74-77 8 75.5 0 0
77-80 7 78.5 3 21
80-83 4 81.5 6 24
83-86 2 84.5 9 18
 

\sum f_i

=30 

    

\sum f_ix_i

=12

Mean, 

\overline x =a + \frac{\sum f_id_i}{\sum f_i}
= 75.5 + \frac{12}{30} = 75.5 + 0.4 = 75.9
Therefore, the mean heartbeats per minute of these women are 75.9

Posted by

HARSH KANKARIA

View full answer

Let the assumed mean be a = 75.5

 

No. of heartbeats

per minute   

Number of

women f_i

Class mark

x_i

 d_i = x_i -a f_id_i
65-68 2 66.5 -9 -18
68-71 4 69.5 -6 -24
71-74 3 72.5 -3 -9
74-77 8 75.5 0 0
77-80 7 78.5 3 21
80-83 4 81.5 6 24
83-86 2 84.5 9 18
 

\sum f_i

=30 

    

\sum f_ix_i

=12

Mean, 

\overline x =a + \frac{\sum f_id_i}{\sum f_i}
= 75.5 + \frac{12}{30} = 75.5 + 0.4 = 75.9
Therefore, the mean heartbeats per minute of these women is 75.9

Posted by

HARSH KANKARIA

View full answer

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