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The following is the frequency distribution of duration for100 calls made on a mobile phone :

Duration (in seconds) Number of calls
95-125
125-155
155-185
185-215
215-245
14
22
28
21
15

Calculate the average duration (in sec) of a call and also find the median from cumulative frequency curve.
 

Answers (1)

best_answer

Answer. [170]

Solution.

Duration fi xi u_{i}\frac{\left ( x_{i}-a \right )}{h} fiui
95-125 14 110 -2 -28
125-155 22 140 -1 -22
155=185 28 170 = a 0 0
185-215 21 200 1 21
215-245 21 230 2 30
  \sum f_{i}= 100     \sum f_{i}u_{i}= 1

a = 170, h = 30
Average = a+\frac{\sum f_{i}u_{i}}{\sum f_{i}}\times h= 170+\frac{1}{100}\times 30= 170+0\cdot 3= 170\cdot 3

less than type
Duration Number of calls
less than 95
less than 125
less than 155
less than 185
less than 215
less than 245
0
0+14 = 14
14+22 =36
36 + 28 = 64
64 + 21 = 85
85 + 15 =100

n = 100

\frac{n}{2}= \frac{100}{2}= 50
median is 170

Posted by

infoexpert27

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