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  • Find the mean marks of students for the following distribution : Marks Number of students 0 and above 10 and above 20 and above 30 and above 40 and above 50 and above 60 and above 70 and above 80 and above 90 and above 100 and above 80 77 72

Find the mean marks of students for the following distribution

Marks Number of students
0 and above
10 and above
20 and above
30 and above
40 and above
50 and above
60 and above
70 and above
80 and above
90 and above
100 and above		 80
77
72
65
55
43
28
16
10
8
0

 

Answers (1)

Answer. [51.75]

Solution. Here we calculate mean by following the given steps:

  1. Find the mid point of each interval.
  2. Multiply the frequency of each interval by its mid point.
  3. Get the sum of all the frequencies (f) and sum of all the (fx)
  4. Now divide sum of (fx) by sum of (f)
     
    Marks xi cf fi fixi
    0-10 5 80 80-77 = 3 15
    10-20 15 77 787-72 = 5 75
    20-30 25 72 72-65 =7 175
    30-40 35 65 65-55 = 10 350
    40-50 45 55 55-43 = 12 540
    50-60 55 43 43-28 = 15 825
    60-70 65 28 28-16 = 12 780
    70-80 75 16 16-10 =6 450
    80-90 85 10 10-8 = 2 170
    90-100 95 8 8-0 = 8 760
          \sum f_{i}= 80 \sum f_{i}x_{i}= 4140

    mean\left ( \bar{x} \right )= \frac{\sum f_{i}x_{i}}{\sum f_{i}}= \frac{4140}{80}= 51\cdot 75

Posted by

infoexpert27

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