Question

in statistic the mean of 25 observation is 10.22. letter on, it was detected that on observation was taken as(-10) instead of 10. find the correct mean

Answer 1

mean of 25 observations = sum of all terms/no. of terms
10.22 = sum of all terms/25
sum of all terms = 10.22 x 25
sum of all terms = 255.5 (1)

If observation was taken as(-10) instead of 10 then the sum of all terms becomes
correct sum of all terms=sum of all terms - (-10) + 10
= sum of all terms + 10 + 10
= sum of all terms + 20
Now by (1),
correct sum of all terms = 255.5 + 20
= 275.5

Correct mean = correct sum of all terms/25
Correct mean = 275.5/25
Correct mean = 11.02