Question

The mean of marks obtained by 100 students was found to be 40.Later on it was discovered that a score of 53 was misread as 83.Find the correct mean.

Answer 1

Hey there!

Mean of 100 students marks = 40 .

Sum of 100 students marks = 4000

Now, Difference between correct one and misread one = -30 .

Now, Actual sum = 4000- 30 = 3970 .

Correct mean = 3970/100 = 39.7

Answer 2

sum of marks obtained by students / no. of students
= mean
so , given incorrect mean = 40
no. of students = 100
incorrect sum of marks obtained by students = 40*100 = 4000
since one reading 53 misread as 83 so ,
correct sum = 4000-83+53= 3970
so correct mean = correct sum / no. of students
= 3970/100 = 39.7