Find the standard deviation for the given sample data. Round your answer to one more decimal place than the original data.
$\begin{array}{lllllllll}18& 18& 18& 9& 15& 5& 10& 5& 15\end{array}$
A. 1.6
B. 5.4
c. 5.1
D. 5.8

Step 1 ：Calculate the mean (average) of the data set: $\frac{18+18+18+9+15+5+10+5+15}{9}=12.555555555555555$

Step 2 ：Subtract the mean from each data point and square the result: $(18-12.555555555555555{)}^2,(18-12.555555555555555{)}^2,(18-12.555555555555555{)}^2,(9-12.555555555555555{)}^2,(15-12.555555555555555{)}^2,(5-12.555555555555555{)}^2,(10-12.555555555555555{)}^2,(5-12.555555555555555{)}^2,(15-12.555555555555555{)}^2$

Step 3 ：Calculate the mean of these squared differences: $\frac{29.641975308641978+29.641975308641978+29.641975308641978+12.641975308641975+5.975308641975309+57.08641975308642+6.530864197530863+57.08641975308642+5.975308641975309}{9}=26.02469135802469$

Step 4 ：Take the square root of the result: $\sqrt{26.02469135802469}=5.101440125888443$

Step 5 ：Round the result to one more decimal place than the original data: $5.101440125888443\approx \boxed{{\displaystyle 5.1}}$