Multiple choice

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

  1. $\displaystyle\frac{nM-a}{4}$
  2. $\displaystyle\frac{nM+a}{2}$
  3. $\displaystyle\frac{nM-a}{2}$
  4. $nM+a$
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A Correct answer
Explanation

Sum of n observations = nM. Sum of n-4 observations = a. Sum of remaining 4 = nM - a. Mean of remaining 4 = (nM - a) / 4.

AI explanation

The total sum of all n observations is n multiplied by M. The sum of the remaining 4 observations is the total sum minus the sum of the n-4 observations, which is nM minus a. The mean of these remaining 4 observations is their sum divided by 4, resulting in the expression (nM-a)/4.

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