The hypothesized relative strategy was confirmed for the unstructured numerical scale but the hypothesized absolute strategy was not confirmed for the scale using only verbal categories the strategy appeared to have relative elements. Stimulus equalizing bias was used as a tool to make a preliminary investigation into the cognitive strategies involved for the two versions of the scale. The results for this scale showed a greater similarity to the version of the 9-point scale consisting only of verbal categories than the unstructured numerical version. For comparison, a 9-point hedonic scale including both verbal categories and numbers together, was also used. To check that the difference was not caused by the fact that the verbal categories were bipolar and the numbers unipolar, the experiment was repeated using a bipolar number scale (–4 through 0 to +4). It also suggested that consumers were using different cognitive strategies for verbal categories and numbers. This indicated that numerical data obtained from both types of 9-point scale were not interchangeable.
NET SENSITIVITY OF SEQUENTIAL TESTING SERIES
To illustrate this, consumers rated five chocolates, in a series of experiments, on these two types of 9-point scale (verbal categories only vs numbers only) and the proportion responding differently to the two scales ranged from 100% to 79%. Foods that were placed in the same verbal category for the former scale might be given different numerical scores on the second scale. The former scale requires consumers to categorize foods according to how much they are liked or not the latter requires the consumers to differentiate numerically between the foods in terms of the relative degree of liking for each. Yet, sometimes what is termed a 9-point hedonic scale is an unstructured numerical scale, labeled at the ends with ‘dislike extremely’ and ‘like extremely’. For subsequent quantitative and statistical analysis, the verbal categories are generally converted to numerical values: ‘like extremely’ as ‘9’, ‘dislike extremely’ as ‘1’. army for menu planning for their canteens, consisted of a series of nine verbal categories representing degrees of liking from ‘dislike extremely’ to ‘like extremely’. The original 9-point scale, developed by the U.S. Side-by-side protocol was less sensitive in cases where sensory fatigue was a factor. In most cases, the side-by-side protocol was more sensitive, thus providing the same information with fewer panelists. Hedonic liking scores were subjected to statistical power analyses and used to calculate minimum number of panelists required to achieve varying degrees of sensitivity when using side-by-side and sequential monadic protocols. The different results obtained by the 2 protocols in order of liking and significance of paired comparisons were due to the experimental variation and differences in sensitivity. Of the 50 pairwise overall liking comparisons, 44 were in agreement. Slight differences in order of overall liking for the other 2 products were not significant. For 3 of the products, both protocols yielded the same order of overall liking. Without their knowledge, panelists rated the same 5 retail brands by 1 protocol and then 3 wk later by the other protocol. Five commercial brands, having a broad quality range, were selected as samples for each product category to assure a wide array of consumer liking scores. Evaluations were conducted on orange juice, frankfurters, canned chili, potato chips, and applesauce. In the sequential monadic evaluation, 1 sample was presented and evaluated on all characteristics, then returned before panelists received and evaluated another sample. In the side-by-side evaluation, all samples were presented at once and evaluated together 1 characteristic at a time. The relative sensitivity of side-by-side and sequential monadic consumer liking protocols was compared.
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