From: "David Mobley" <[EMAIL PROTECTED]>
Reply-To: Discussion list for GROMACS users <gmx-users@gromacs.org>
To: "Discussion list for GROMACS users" <gmx-users@gromacs.org>
Subject: Re: [gmx-users] error estimates of free energy calculations
Date: Tue, 15 May 2007 15:55:01 -0700
Jeroen,
However, in my opinion (assuming the total error should be calculated
from standard error propagation), the way g_analyze calculates the
total error is incorrect. It results in an overestimation of this
total error by at least a factor of sqrt((number of lambda points) -
1). This factor is 4.5 in my case, accounting for the larger part of
my previoulsy mentioned loss of accuracy. And indeed, as you guys
already mentioned, the remaining part may be explained from the fact
that Berk uses twice as many lambda values.
Whoops! Justifies my paranoia about using other people's analysis
tools. :) The person responsible for the analysis tool should take a
look at this -- if the tool does error analysis for the integral, it
should do it properly.
ah, g_analyze indeed seems to print an error estimate of the integral,
I didn't know about this.
But according to me this is totally wrong.
It divides the sum of variances by n-1, whereas this should be n^2.
I'll fix it for the next release.
Berk.
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