commonly used method for determining the reactivity ratios of a copolymerization reaction is by linearization of the Mayo-Lewis equation, such as those first pioneered by Fineman and Ross [6] and Kelen and Tudos. [7] Such methods, however, have been found to alter the error structure of the collected data, giving statistically incorrect results, [8] and are still in use to this day. [9-14] This problem was solved with the use of nonlinear parameter estimation techniques, such as the error-in-variables method (EVM), which are based on sound statistical theory (Bayesian approach) and return parameter estimates with joint confidence regions. [15,16] For metallic catalyzed copolymerizations the ratios can be calculated by directly using monomer kinetic propagation parameters combined with specialized molecular weight distribution deconvolution software. [17] Part of the reason for why methods such as Fineman-Ross and Kelen-Tudos are still used to this day is not only due to their ease of use and traditional weight but also because of a lack of widespread and publicly available alternatives that can be used and modified freely to tackle specific problems. This work seeks to lessen the lack of availability of these more statistically sound methods so that others may use and further contribute to their development in a free environment, in particular of EVM. Besides the reports of the groups who worked on the early development of EVM, [18-21] other groups worked on their own implementations of EVM. [22-24] None of these codes is easily accessible. Poly[(itaconic acid)-co-(N-vinyl-2-pyrrolidone)] (PVPIA) is reported as being a hydrophilic, highly biocompatible copolymer [25] that, when synthesized in the presence of a crosslinker or through UV or gamma-ray irradiation, produces a crosslinked hydrogel that may present swelling rates of up to 1500%. [26] It can be used as a heavy metal ion remover in waste-water treatment, [27,28] as an enzyme immobilization support structure, [29] and as a medium for the controlled release of drugs. [30] It is also worth noting that except for applications as a heavy metal ion remover in waste-water treatment, [27,28] the Itaconic Acid content used was below 10% (between 3% and 8%) of the total initial monomer charge. However, reports of the copolymer when prepared through free radical chain polymerization are severely limited and so are descriptions of its physical properties and possible applications. Designed copolymers require an understanding of the relative reactivity ratios of the monomer pair and a proper regression technique that can extract this data from the experiments. An implementation of the error-in-variables method previously describes in the literature is written and made available for use, along with an high-performance liquid chromatography (HPLC) methodology for acquiring the kinetic data for the regression analysis of the itaconic acid and N-vinyl-2-pyrrolidone (IA/NVP) free-radical copolymerization system. From the data, it is observed that higher initial mole fract...