Question

the calculated meaning of 50 observation was 80 . it was later discovered that observation 19 was recorded by mistake as 91 .what was the correct mean?

Answer 1

the mean of 50 observation = 80
Then, sum of the total observation =50×80=4000
Now observation 19 was recorded by mistake as 91
Therefore,
Total sum =4000-91=3909
Now we add 19 in the total sum .
Hence,Total sum =3909+19=3928
Now correct Mean =3928÷50=78.56