ENBIS-17 in Naples

9 – 14 September 2017; Naples (Italy) Abstract submission: 21 November 2016 – 10 May 2017

Bayesian Thinking in the Cosmetic Industry

12 September 2017, 18:20 – 18:40


Submitted by
Philippe Bastien
Philippe Bastien (L'Oréal R&D), Charles Gomes (L'Oréal R&D)
Many scientific institutions have recently questioned the reproducibility issue of scientific results. They stressed the misuse of the p-value, which is contributing to the number of research findings that cannot be reproduced. To address this issue, The American Statistical Association recommends supplementing p-values with other approaches which include Bayesian methods. This is currently in practice at L'Oréal for the Proof of Concept Studies and will be described based on results from a Whitening study.
This approach gives a greater place to the expertise through the definition by the clinicians of classes of performance for the parameters of interest, taking better account of the effect size in the interpretation of the results. Determining the probabilities of belonging to each of the performance classes provides much more information than the binary rule associated with the p-value. It will also allow to define efficiency profiles for the actives and to rank them accordingly. Moreover, reproducibility issue can be addressed using Bayesian power to determine the probability a future study will be successful based on results from a previous one. If success is associated to a significant comparison, this corresponds to the notion of Assurance, but success can be any other decision rule in a full Bayesian approach. In the example shown, a success will be defined by the probability of belonging to a performance class higher or equal to a specified threshold. Incorporation of prior information, whether it is from expert opinion or historical data will be also discussed.
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