Reconsidering the Specified Tetrad Test

• Published in: Journal of sensory studies Vol. 28; no. 6; pp. 445 - 449
• Main Authors: Garcia, Karen, Ennis, John M., Prinyawiwatkul, Witoon
• Format: Journal Article
• Language: English
• Published: Cincinnati Blackwell Publishing Ltd 01.12.2013; Wiley Subscription Services, Inc
• ISSN: 0887-8250; 1745-459X
• DOI: 10.1111/joss.12060

Additional noise from additional stimuli has been shown to result in a loss of operational power in sensory difference tests. Because the Specified Tetrad test requires the evaluation of four stimuli and has only a slight theoretical power advantage over the two‐alternative forced choice (2‐AFC), Ennis and Jesionka have argued that the Specified Tetrad test should not be used. But this theoretical assertion had not been confirmed experimentally. In this article, we refute this argument using results from a large‐scale comparison of the 2‐AFC with the Specified Tetrad test. Using Thurstonian analysis, we quantified the sensory effect size as measured by both tests and found that the Specified Tetrad test is significantly more sensitive than the 2‐AFC in this setting. In fact, if the sample values from our experiment could be taken as population values, the results of this experiment predict that the Specified Tetrad test is operationally more powerful than a double‐replicated 2‐AFC. While further investigation of the Specified Tetrad test is needed before such a strong statement can be confirmed, these results indicate that the Specified Tetrad test is worthy of such investigation. Practical Applications Among the many tools in the sensory scientist's tool box are the specified difference testing methods. These methods can be used when the attribute that defines the difference between the samples is known. Historically, the 2‐AFC has been considered the operationally most powerful method of specified testing, but the 2‐AFC has never been compared with the Specified Tetrad test. In this article, we provide such a comparison, and show that the Specified Tetrad test deserves attention as a specified testing method.