Sorry Ian, I was attributing this to Kevin apologies Phil
> On 12 Mar 2017, at 21:56, Ian Tickle <ianj...@gmail.com> wrote: > > > Eleanor, > > Phil is right about the bias of the weighted mean, here's how I do it using a > minimum mean-squared error estimator which seems to give more accurate > results than either the unweighted or the weighted mean: > > http://staraniso.globalphasing.org/Optimal-F-estimator.pdf > > This is actually about Fmean but the same applies to Imean. > > This actually only makes a significant difference to the result if there's a > big difference between sd(I+) and sd(I-), which is obviously not very common. > > Cheers > > -- Ian > > > > On 12 March 2017 at 17:58, Eleanor Dodson <eleanor.dod...@york.ac.uk> wrote: > You read: > h k l IPLUS SIGIPLUS INEG SIGINEG > Then program calculates this: > > SIGIMEAN = SIGIPLUS*SIGINEG/(SIGIPLUS+SIGINEG) > > IMEAN = (IPLUS/SIGIPLUS + INEG/SIGINEG)*SIGIMEAN > > ie: IMEAN = ( IPLUS*SIGINEG + INEG * SIGIPLUS ) / /(SIGIPLUS+SIGINEG) > > Is that the right thing to do? Not sure! > > Eleanor Dodson > > > > On 11 March 2017 at 15:18, Karthikeyan Subramanian <skarthi...@gmail.com> > wrote: > Dear CCP4bb, > > How IMEAN and SIGIMEAN is calculated in scalepack2mtz if the input is with > anomalous intensity (obtained from HKL2000). Any guide/reference is highly > appreciated. > > Thanks in advance, > > With regards > > Karthikeyan S. > > Principal Scientist > > IMTECH, Chandigarh > >