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 $\frac{3}{5}$

Given $\sum x_i=12,\sum x_i^2=18,n=10$
Hence Standard deviation is $=\sqrt{\frac{\sum x_i^2}{n}-{\left(\frac{\sum x_i}{n}\right)}^2}=\sqrt{\frac{18}{10}-{\left(\frac{12}{10}\right)}^2}=\frac{3}{5}$