“…Bhatia and Loomes (2017) explore the effects of random variation in parameters of a decision making model, but note that such variation cannot explain all of the phenomena of choice data, so there must be another source of error. This article will expand upon an approach based on True and Error (TE) theory (Birnbaum, 2011(Birnbaum, , 2013(Birnbaum, , 2019Birnbaum & Bahra, 2007a, 2012a, 2012bBirnbaum & Diecidue, 2015;Birnbaum & Gutierrez, 2007;Birnbaum & Schmidt, 2008;Birnbaum, Schmidt & Schneider, 2017;Birnbaum & Quispe-Torreblanca, 2018). This approach does allow separation (and estimations) of the variability due to changes in true preferences and due to random errors.…”