http://en.wikipedia.org/wiki/Propagation_of_uncertainty From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of capricy gao Sent: Saturday, June 04, 2011 10:45 AM To: [log in to unmask] Subject: [ccp4bb] Question about the statistical analysis-might be a bit off topic If means and standard deviations of A and B are known, how to estimate the variance of A/B? Thanks.