Comparing taste-test rating protocols. Taste-testers of new food products are presented with several competing food samples and asked to rate the taste of each on a 9-point scale (where 1 =“dislike extremely” and 9 =“like extremely”). In the Journal of Sensory Studies (June 2014), food scientists compared two different taste-testing protocols. The sequential monadic (SM) method presented the samples one-at-a-time to the taster in a random order, while the rank rating (RR) method presented the samples to the taster all at once, side-by-side. Consider the following experiment (similar to the one conducted in the journal): 50 consumers of apricot jelly were asked to taste-test five different varieties. Half the testers used the SM protocol and half used the RR protocol during testing. In a second experiment, 50 consumers of cheese were asked to taste-test four different varieties. Again, half the testers used the SM protocol and half used the RR protocol during testing. For each product (apricot jelly and cheese), the
- a. Consider the five varieties of apricot jelly. Identify the varieties for which you can conclude that “the mean taste scores of the two protocols (SM and RR) differ significantly at α = .05.”
- b. Consider the four varieties of cheese. Identify the varieties for which you can conclude that “the mean taste scores of the two protocols (SM and RR) differ significantly at α = .05.”
- c. Explain why the taste-test scores do not need to be
normally distributed for the inferences, parts a and b, to be valid.
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