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 >> > >
