Question

The mean of 40 observations was 160. It was detected on rechecking that the value of 165 was wrongly copied as 125 for computation of mean. Find the correct mean.

Answer 1

Here,

$n=40,\overline{X}=160$

So, $\overline{X}=\frac{1}{n}(\sum x_i)$

$160=\frac{1}{40}(\sum x_i)$

$\sum x_i=6400$

Therefore, incorrect value of $\sum x_i=6400$

Now,

Correct value of $\sum x_i=6400-125+165=6440$

Therefore,

Correct mean = $\frac{6440}{40}=161$