The mean of the marks scored by 50 students was found to be 39. Later on it was discovered that a score of 43 was misread as 23. The correct mean is
Given,
No. of students = 50
Mean marks secured by them = 39
Incorrect sum of marks secured = 39 × 50 = 1950.
Correct sum = incorrect sum – (incorrect marks) + correct marks
= 1950 – 23 + 43 = 1970
Correct mean = 
39.4.
18