Question

If the sum and sum of squares of $10$ observations are $12$ and $18$ resp., then, The $S.D$ of observations is :-

• A. $\frac{1}{5}$
• B. $\frac{2}{5}$
• C. $\frac{3}{5}$
• D. $\frac{4}{5}$

Answer 1

The correct option is C $\frac{3}{5}$

$\sum x=12,\sum x^2=18,N=10$

$SD=\sqrt{\frac{\sum x^2}{N}-(\frac{\sum x}{N}{)}^2}$

$⟹SD=\sqrt{\frac{18}{10}-(\frac{12}{10}{)}^2}=\frac{3}{5}$