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Ishii R.,University of California at Davis | O'Mahony M.,University of California at Davis | Rousseau B.,Institute for Perception
Food Quality and Preference | Year: 2014

The objective of this research was twofold: first, the performance of the tetrad protocol was compared to that of the triangle test under conditions that could possibly lower its sensitivity, consequently resulting in the loss of its theoretical power advantage. Second, the same samples were compared with a preference test to investigate whether a no difference conclusion obtained with a discrimination test would consistently result in a non-significant preference (consumer relevance).The investigation involved sensory differences that could be deemed small (d' values less than 1.0) as well as the comparison of resampling vs. no resampling conditions. 456 consumers performed tests using apple and orange juices for which slight sensory differences were created through dilution. In all conditions, the tetrad always exhibited a greater number of correct answers than the triangle, confirming its greater statistical power. Therefore, it was concluded that even for small sensory differences, and in conditions where sensory fatigue could play a greater role (resampling allowed), the tetrad test sill appears like a good alternative to the triangle. Also, the theoretical increase in performance predicted when allowing sample resampling was confirmed.For the preference study, the same stimuli were evaluated by 208 subjects. Consumer relevance was defined as a significant result between two products in a preference test (assuming no population segmentation). Such significant preferences were found for three out of the four conditions, including the one with the smallest difference for which a significant result had not been found with either the tetrad or triangle. The non-significant preference in the fourth condition was attributed to segmentation in the population.Therefore, this investigation confirmed further that the tetrad test is a viable alternative to the triangle test, as it exhibits a greater statistical power even in conditions that could potentially affect it negatively. Also, it was shown that a non-significant sensory difference can still result in a significant preference test, outlining the necessity to go beyond the simple use of a 'more powerful' discrimination test when making decisions and to define the actual consumer relevance of an underlying sensory difference. © 2013 Elsevier Ltd.

Ennis J.M.,Institute for Perception | Rousseau B.,Institute for Perception | Ennis D.M.,Institute for Perception
Journal of Sensory Studies | Year: 2014

In the evaluation of new incarnations of existing products, difference testing is among the most commonly used sensory techniques. However, although difference testing is a classical technique, the science of difference testing continues to evolve. As Thurstonian analysis has gained increased acceptance for its ability to measure sensory differences, recent research advances have provided tools, techniques and theory to view sensory difference tests as measurement instruments. In particular, these advances promise to unite equivalence and difference testing, to help with the determination of consumer-relevant action standards, and to inform business risk calculations. © 2014 Wiley Periodicals, Inc.

Jervis S.M.,North Carolina State University | Ennis J.M.,Institute for Perception | Drake M.A.,North Carolina State University
Journal of Sensory Studies | Year: 2012

Adaptive choice-based conjoint (ACBC) analysis is a technique that uses choice data and incorporates it into an adaptive interviewing experience. ACBC analysis has been suggested to provide more accurate information at the individual level, which can lead to better predictions even when using smaller sample sizes. A comparison of a traditional choice-based conjoint (CBC) survey and an ACBC survey was undertaken to compare the overall utility scores and importance values of attributes determined by both techniques using sour cream as the subject. A CBC and an ACBC survey were conducted. More respondents participated in the CBC (n=777) survey than in the ACBC version (n=250). Respondents to the ACBC version were from the same pool of respondents to the CBC version. A random sample of 250 respondents from the CBC survey was also analyzed. Results were analyzed by overall utility scores, importance values, landscape segmentation analysis and cluster analysis via latent class. The ACBC and CBC results were similar in overall utility scores for all attributes with similar respondent clusters. Both techniques revealed fat content as the most important attribute, followed by price and followed by brand. The CBC result for 250 respondents overestimated the importance of brand. The ACBC utility scores were not as distinct as CBC results in all categories; however, the direction of the mean utility scores was the same in all categories. Overall, ACBC and CBC revealed similar outcomes for different sour cream product types when price was excluded; however, the CBC results differentiated products to a greater extent than ACBC with the same sample size considered. © 2012 Wiley Periodicals, Inc..

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