In the previous exercise you found the variance of these particular values:
The standard deviation is the square root of this:
Starting from scratch the working would be:
5 
4 
3 
2 
5 
5 
The formula is:
The mean was calculated previously, and equals 4.
i 


1 
5 
1 

2 
4 
0 

3 
3 
1 

4 
2 
4 

5 
5 
1 

6 
5 
1 

4 
8 

1.26 