Question

The number of refrigerators sold in 5 consecutive days are 4, 5, 9, 10, 12. Find the standard deviation of the number of refrigerators sold using Direct method.

• A. 3.03
• B. 4.21
• C. 6.32
• D. 4.56

Answer 1

The correct option is A 3.03

$\begin{array}{cc}xi& x{i}^2\\ 4& 16\\ 5& 25\\ 9& 81\\ 10& 100\\ 12& 144\\ \sum xi=40& \sum x{i}^2=366\end{array}$

Standard Deviation

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

$=\sqrt{\frac{366}{5}-(\frac{40}{5}{)}^2}$

$=\sqrt{73.2-64}$

$=\sqrt{9.2}=3.03$