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Evaluating Wine-Tasting Results and Randomness with a Mixture of Rank Preference Models*

Published online by Cambridge University Press:  25 February 2015

Jeffrey C. Bodington*
Affiliation:
Bodington & Company, 50 California St. #630, San Francisco, CA 94111; e-mail: [email protected].

Abstract

Evaluating observed wine-tasting results as a mixture distribution, using linear regression on a transformation of observed results, has been described in the wine-tasting literature. This article advances the use of mixture models by considering that existing work, examining five analyses of ranking and mixture model applications to non-wine food tastings and then deriving a mixture model with specific application to observed wine-tasting results. The mixture model is specified with Plackett-Luce probability mass functions, solved with the expectation maximization algorithm that is standard in the literature, tested on a hypothetical set of wine ranks, tested with a random-ranking Monte Carlo simulation, and then employed to evaluate the results of a blind tasting of Pinot Gris by experienced tasters. The test on a hypothetical set of wine ranks shows that a mixture model is an accurate predictor of observed rank densities. The Monte Carlo simulation yields confirmatory results and an estimate of potential Type I errors (the probability that tasters appear to agree although ranks are actually random). Application of the mixture model to the tasting of Pinot Gris, with over a 95% level of confidence based on the likelihood ratio and t statistics, shows that agreement among tasters exceeds the random expectation of illusory agreement. (JEL Classifications: A10, C10, C00, C12, D12)

Type
Articles
Copyright
Copyright © American Association of Wine Economists 2015 

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Footnotes

*

The author thanks an anonymous reviewer and Professor Thomas Brendan Murphy, School of Mathematical Sciences at University College Dublin for their helpful comments. All remaining errors and omissions are the responsibility of the author alone.

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