Given:
The data is,
[tex]11,12,4,9,4[/tex]
First, find the mean of the given data set,
[tex]\bar{x}=\frac{11+12+4+9+4}{5}=\frac{40}{5}=8[/tex]
The standard deviation of the data is calculated as,
[tex]\begin{gathered} s^2=\frac{\sum^5_{i\mathop=1}(x_i-\bar{x})^2}{n-1} \\ s^2=\frac{(11-8)^2+(12-8)^2+(4-8)^2+(9-8)^2+(4-8)^2}{5-1} \\ s^2=\frac{58}{4} \\ s=\: 3.81 \end{gathered}[/tex]
Answer: standard deviation is 3.81
