Question

Mean of 100 observations was found to be 30. At time of re checking 2observations were taken as 32 and 12 instead of 23 and 11 find correct mean

Answer 1

let the obs are x1,x2,......x100
mean=x1+x2+......+x100/100
=>3000=x1+x2+....+x100
since two variable are wrong
x1+x2+....+x100=3000+23+11-32-12
=2990
so ,mean=2990/100
=29.90