Question

The number of bridges constructed in 5 consecutive months are 1,2,3,4,5. Find the Standard deviation of the number of bridges constructed using Direct method.

• A. 1.41
• B. 2.14
• C. 3.21
• D. 4.28

Answer 1

The correct option is A 1.41

$\begin{array}{cc}xi& x{i}^2\\ 1& 1\\ 3& 4\\ 3& 9\\ 4& 16\\ 5& 25\\ \sum xi=15& \sum x{i}^2=55\end{array}$

Standard Deviation

$\sigma =\sqrt{\frac{\sum x{i}^2}{n}-(\frac{\sum xi}{n}{)}^2}$

$=\sqrt{\frac{55}{5}-(\frac{15}{5}{)}^2}$

$=\sqrt{11-9}$

$=\sqrt{2}=1.41$