Question

If the mean of observations x, x + 2, x + 4, x + 6 and x + 8 is 11, find:
(i) The value of x;
(ii) The mean of first tree observations. Solution.

• A. (i) 7
  (ii) 9
• B. (i) 7
  (ii) 10
• C. (i) 8
  (ii) 9
• D. (i) 8
  (ii) 10

Answer 1

The correct option is A (i) 7

(ii) 9
It is given that mean of observations x, x + 2. x + 4, x + 6 and x + 8 is 11
We know that
$\text{Mean}=\frac{\text{Sum of observations}}{\text{Number of observations}}\Rightarrow 11=\frac{x+x+2+x+4+x+6+x+8}{5}\Rightarrow 11=x+4\Rightarrow x=7\left(i\right)\left(ii\right)\text{Mean of first three observations}=\frac{x+x+2+x+4}{3}=x+2=9$