Comparison of experimental Stated Choice (SC) designs is important in appropriately using different designs for any given context. The importance of using appropriate experimental designs is due to the impact that experimental designs have in accurately estimating model parameters, standard errors and derived measures, such as Willingness-To-Pay and Welfare. Despite the existence and use of a variety of SC designs, the health economic literature reports the use of predominantly fractional factorial orthogonal designs. This study extends existing design literature by using varying literacy levels as proxies for respondents' cognitive ability to investigate the 'robustness' of fractional factorial orthogonal and efficient designs to choice task simplification. Comparing the robustness of designs helps to further explain why designs provide differing standard error parameter estimates.