Question

Mean marks obtained by 100 students are estimated to be 40. Later on its is found that one value was read as 83 instead of 53.
Find out the 'corrected' mean.

Answer 1

`barX=(sumX)/N`
Or, `sumX=barXN`
Given: `barX=40,N=100`
`40=(sumX)/100`
`:.sumX"(wrong)"=40xx100=4,000`
Correct value = 53
Incorrect value=83
Correct
`barX=(sumX"(Wrong)+(Correct value)-(Incorrect value)")/N`
`=(4,000+53-83)/100`
`=(3,970)/100=39.70`
Thus, Corrected Mean = 39.70.