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Find the mean and mode for the following data : 

class 10-20 20-30 30-40 40-50 50-60 60-70 70-80
frequency  4 8 10 12 10 4 2

 

 

 

 
 
 
 
 

Answers (1)

 

class  frequency  x Fx
10-20 4 15 60
20-30 8 25 200
30-40 10 35 350
40-50 12 45 540
50-60 10 55 550
60-70 4 65 260
70-80 2 75 150
  50   2110

Formula to calculate mean 

Mean , 

\bar { X} = \frac{\Sigma X i F i }{\Sigma f i } \\\\ = \frac{2110 }{50} = 42.2\\\\

Formula to calculate mode 

mode = l + \frac{f _1 - f _0 }{2 f _ 1 - f_0 - f _2 }\times h \\\\ l = 40 , f _1 = 12 , f _ 2 = 10 , f _ 0 = 10 , h = 10 \\\\ = 40 + \frac{12-10 }{2\times 12-10-10} \times 10 \\\\ = 40 + \frac{2}{24-20} \times 10 \\\\ 40 + 5 \\\\ = 45

Therefore mean is 42.2 and mode is 45 

Posted by

Safeer PP

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