[gmx-users] Reg: Standard error

[Mark Abraham]

On 1/12/2010 7:59 PM, vinothkumar mohanakrishnan wrote:
> Hi Gromacians
>
> I am planning to compute the standard error for the interfacial 
> surface tension of water-dichloro ethane. i just want to know is my 
> procedure right. below is the result what i get from my g_energy command.
>
> Statistics over 500001 steps [ 0.0000 thru 1000.0001 ps ], 1 data sets
> All averages are exact over 500001 steps
>
> Energy                      Average       RMSD     Fluct.      Drift  
> Tot-Drift
> -------------------------------------------------------------------------------
> #Surf*SurfTen               692.904    4579.46    4579.16  -0.181601   
> -181.602
>
> my question is to calculate the standard error should i need to divide 
> the RMSD(4579.46) by the squareroot of 500001 steps? any help is 
> highly appreciated.

Calculating the standard error of the mean in this way requires that the 
observations are independent 
(http://en.wikipedia.org/wiki/Standard_error_%28statistics%29). Adjacent 
MD frames are not. You would need to know something about your 
correlation times to know how long you have to wait before effective 
independence.

Mark