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What is the assume mean method, …

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What is the assume mean method, with example
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Sia ? 4 years, 10 months ago

For calculating arithmetic mean from this data, We have to first take the midpoint of each class interval, represented by 'm' in the table. Then decide on anyone midpoint as assumed mean and find out the deviations.

Calculation of Arithmetic Mean

<th scope="col">Marks</th> <th scope="col">Number of Students (f)</th> <th scope="col">Mid-Value (m)</th> <th scope="col">dm (m-A) A=45</th> <th scope="col">fdm</th> <th scope="col"> </th>
10-20 2 15 -30 -60 -300
20-30 7 25 -20 -140
30-40 10 35 -10 -100
40-50 15 45 0 0  
50-60 20 55 +10 +200 +700
60-70 16 65 +20 +320
70-80 6 75 +30 +180
  {tex}\Sigma f = 76{/tex}       {tex}\Sigma f d m = + 400{/tex}
 

After multiplying fd with m for all the values and finding the total of fdm, we apply the values to the formula of mean given below:

Now, {tex}\overline { X } = A + \frac { \Sigma f d m } { \Sigma f } \Rightarrow \overline { X } = 45 + \frac { 400 } { 76 }{/tex}
{tex}\Rightarrow \quad \overline { X } = 45 + 5.26 = 50.26{/tex}

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