Question

The mean of 20 observations is 45.by an error one observation is registered as 52 instead of 25 .find the correct mean

Answer 1

Let S be the Sum of all observation except INCORRECT one
then
$mean \: = (s + 52) \div 20$
45 ×20 =S + 52
848 =S
Let
Correct Mean = MC
then
$mc \: = (s + 25) \div 20$
mc = (848 +25)÷20
mc = 873÷20
mc = 43.65 ( Correct Mean )