Estimating intensity errors of powder diffraction data from area detectors

It is shown how error estimates for intensities derived from area detector data in powder diffraction experiments should be calculated. It is demonstr ated that the uncritical application of standard weighting schemes to the d erived one dimensional data in subsequent least-squares refinements results in meaningless goodness of fit values less than unity that prohibit the ev aluation of the quality of the fit. Moreover, it is shown that the calculat ed estimated standard deviations of the fitted parameters can only be calcu lated correctly when the true uncertainties of the measured intensities are known.