Question 60
The mean of 30 observations was calculated as 150. Later, it was pointed out that value of one of the observations was wrongly taken as 135 instead of 165. The correct mean is
Solution
Mean of 30 observations = 150
For correcting the error, we need to subtract 135 and add 165,
=> New average = $$\frac{(150\times30)+165-135}{30}$$
= $$\frac{150\times30+30}{30}$$
= $$150+1=151$$
=> Ans - (B)
