Rt-Rb × 100 and R t = Rt-Rb Rt-Rb × 100. The normalized measurement error i,j is the scaled i,j : i,j = 100 Rt-Rb i,j . Hence, the variance of i,j is σ 2 c = 100 2 ( Rt-Rb ) 2 σ 2 c . Thus, if we use the normalized data {r i,j , x i } for j = 1, . . . , n i and i = 1, . . . , m, the corresponding parameters are θ = (R b , R t , x 50 , H) with R b and R t defined above and x 50 and H remaining the same as in the original formulation. Clearly, using the normalized data and the parameters θ , the model assumption does not change, except for a different notation.