The IDEM estimates the reactivity ratios of multiple-site-type catalysts used to make ethylene/α-olefin copolymers. Analytical data from high-temperature GPC and 13C NMR are required in the estimation process. The CSLD information from the 13C NMR is a crucial step in the estimation method due to NMR sensitivity and probe efficiency. The effect of inter-laboratory analysis on IDEM parameter estimation and model predictions is studied. The copolymer samples are analyzed at the University of Waterloo and Dow Chemical Research Center at Freeport, Texas without standardization. The results prove that the IDEM is a robust parameter estimation model for ethylene/α-olefin copolymers made with multiple-site-type catalysts, even when the copolymer samples are analyzed in different laboratories.