If we assume that the relative standard deviations of all three assays are the same (RSDG), then the three variances are VF,i = [GF,i(RSDG)] 2 , VP,i = [GP,i(RSDG)] 2 = and VT,i = [GT,i(RSDT)] 2 . Substitution of these three expressions into Equation 4 and dividing by RSDG 2 gives: