Question

The mean of 50 observation was 250.It was detecting on checking that the value of 165 was wrongly copied as 115 for compilation of mean.Find the correct mean?

Answer 1

Mean of 50 observations will be given as:
$mean = \frac{sum \: of \: observations}{50}$
so,
$sum = 50 \times mean$
i.e., sum = 50 × 250 = 12500
now , the 165 was wrongly copied as 115, so correcting the sum
sum = 12500 - 115 + 165 = 12,550
now, corrected mean is
mean = 12,550÷50 = 251