Question

Find the mean of the following frequency distribution using the assumed mean method.

Answer 1

Let's assume ‘17’ as the assumed mean,

a = 17 >

Let’s calculate

• $d_i$ which is the deviation of ith class,

$d_i$= $x_i-a$

The deviation of other observations from the assumed mean is given in the table.
Now lets calculate the product of $f_i{d}_i$fidi and then calculate Σ$f_i{d}_i$ and Σ$f_i$.

Σ$f_i{d}_i$ = 72

Σ$f_i$ = 40 >

Now we are so close to finding the solution. Let's use the assumed method formula,
$x=a+\frac{\Sigma fidi}{\Sigma fi}$

$x$= 17 + (72/40)

$x$ = 17 + 1.8

$x$= 18.8