Question:
If the sum of the deviations of 50 observations from 30 is 50 , then the mean of these observation is :
Correct Option: , 4
Solution:
$\sum_{i=1}^{50}\left(x_{i}-30\right)=50$
$\Sigma x_{i}=50 \times 30=50$
$\Sigma x_{i}=50+50+30$
Mean $=\bar{x}=\frac{\sum x_{i}}{n}=\frac{50 \times 30+50}{50}=30+1=31$