Question

The A. M. of n observations is M. If the sum of n - 4 observations is a, then the mean of remaining 4 observations is

• A. $\frac{nM-a}{4}$
• B. $\frac{nM+a}{4}$
• C. $\frac{nM-A}{2}$
• D. $nM+a$

Answer 1

The correct option is A $\frac{nM-a}{4}$

Let mean of the remaining 4 observations be ${\overline{x}}_1$
Then, M =$\frac{s+4{\overline{x}}_1}{(n-4)+4}\Rightarrow \overline{x_1}=\frac{nM-a}{4}$