Question

The number of toys sold for 5 days are given as 1,2,3,4,5.
Find it's standard deviation using mean method.

• A. 1.41
• B. 2.52
• C. 3.25
• D. 4.56

Answer 1

The correct option is A 1.41

Mean
$=\overline{x}=\frac{1+2+3+4+5}{5}=\frac{15}{5}=3$

$\begin{array}{ccc}xi& di=xi-\overline{x}=xi-3& d{i}^2\\ 1& -2& 4\\ 2& -1& 1\\ 3& 0& 0\\ 4& 1& 1\\ 5& 2& 4\\ & & \sum d{i}^2=10\end{array}$

Standard Deviation

$\sigma =\sqrt{\frac{\sum d{i}^2}{n}}$

$=\sqrt{\frac{10}{5}}$

$=\sqrt{2}\simeq 1.41$