Problem:-
mean marks of 100 students was 40.. It was discovered that 53 was misread as 83. Find the actual mean.
Solution:-
Total mean score = 40
[tex]mean \: = \frac{sum \: of \: observation}{number \: of \: observations} [/tex]
sum of observations
= mean × no of observations
= 40×100
= 4000
After the replacement, sum of new observation will be
=4000-83+53
= 3970
mean of new the observation will be
[tex] = \frac{3970}{100} [/tex]
[tex] = 39.7[/tex]
[Hence, the actual mean is 39.7]
