Question

The mean of $20$ observation is $32$. In this data, one observation was taken by mistakes as $52$ instead of $25$. Find the correct mean.

Answer 1

Given that mean of $20$ observations is $32$

No" of observations $=20$

mean $=32$

sum of observations $=20\times 32=640$

Here one observation was taken by mistake as $52$ instead of $25$

Hence correct sum of observation is

$=640-52+25$

$=640-27$

$-613$

Correct mean $=\frac{correctsumofobservations}{No.ofobservations}$

$=\frac{613}{20}$

Correct mean $=30.65$