15.The arithmetic mean of 50 observations was found to be It was later on discovered that it was wrong because an observation of 48 was wrongly taken as What will be the correct mean ?

The correct answer is (b).

The sum of the observations is $50 \times 35.2 = 1760$.
The correct sum is $1760 – 48 + 45 = 1767$.
The correct mean is $\frac{1767}{50} = 35.94$.

Option (a) is incorrect because it is the mean of the incorrect sum.
Option (c) is incorrect because it is the mean of the correct sum plus 1.
Option (d) is incorrect because it is the mean of the correct sum plus 2.