Question:
Find the mean of each of the following frequency distributions :
Solution:
Let the assumed mean be A = 20 and h = 8.
We know that mean, $\bar{X}=A+h\left(\frac{1}{N} \sum f_{i} u_{i}\right)$
Now, we have $N=\sum f_{i}=40, \sum f_{i} u_{i}=5, h=8$ and $A=20$.
Putting the values in the above formula, we have
$\bar{X}=A+h\left(\frac{1}{N} \sum f_{i} u_{i}\right)$
$=20+8\left(\frac{1}{40} \times(5)\right)$
$=20+\frac{40}{40}$
$=20+1$
$=21$
Hence, the mean is 21.
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