On Thu, Oct 16, 2008 at 3:11 PM, Sébastien Morin <[EMAIL PROTECTED]> wrote: > Hi, > > I have a general question about curve fitting within relax. > > Let's say I proceed to curve fitting for some relaxation rates > (exponential decay) and that I have a duplicate delay for error estimation. > > ======== > delays > > 0.01 > 0.01 > 0.02 > 0.04 > ... > ======== > > Will the mean value (for delay 0.01) be used for curve fitting and rate > extraction ? > Or will both values at delay 0.01 be used during curve fitting, hence > giving more weight on delay 0.01 ? > > In other words, will the fit only use both values at delay 0.01 for > error estimation or also for rate extraction, giving more weight for > this duplicate point ? > > How is this handled in relax ? > > Instinctively, I would guess that the man value must be used for > fitting, as we don't want the points that are not in duplicate to count > less in the fitting procedure... Am I right ? >
I would argue not. If we have gone to the trouble of measuring something twice (or, equivalently, measuring it with greater precision) then we should weight it more strongly to reflect that. So we should include both duplicate points in our fit, or we should just use the mean value, but weight it to reflect the greater certainty we have in its value. As I type this I realise this is likely the source of the sqrt(2) factor Tyler and Edward have been debating on a parallel thread - the uncertainty in height of any one peak is equal to the RMS noise, but the std error of the mean of duplicates is less by a factor of sqrt(2). Chris _______________________________________________ relax (http://nmr-relax.com) This is the relax-users mailing list relax-users@gna.org To unsubscribe from this list, get a password reminder, or change your subscription options, visit the list information page at https://mail.gna.org/listinfo/relax-users
