One‐tailed and Two‐tailed Tests in Organoleptic Comparisons

Abstract

Procedures and the basic statistical principles underlying the pairedsample and triangular techniques in organoleptic testing have been described in numerous papers (2, 3, 4,5, 6, 8, ll). These tests are frequently used (a) to determine whether an experimental product differs from a standard in respect to a given character or to select members of a taste panel capable of distinguishing between a product and a standard, and (b) to compare the quality or preference between two products.It is the purpose of this paper to supply tables for paired-sample and triangular tests and to discuss briefly which tables are appropriate for each of the cases (a) and (b).Under case (a) above let us consider the selection of a panel of tasters by means of paired samples. To test the acuity of the group, each taster is given one sample of unsweetened tomato juice and a second sample of the same juice to which a small amount of sucrose has been added. We are interested in the ability of the taster to be able to select "correctly" in a series of trials the sample having the greater sweetness. If he is able to detect this sample with a frequency which will sufficiently exceed that to be expected by chance, then we shall infer that this taster does possess some ability in detecting sugar in tomato juice, provided, of course, that our experimental controls are adequate. If this taster were to select the sweet sample "correctly" with a frequency sufficiently below that expected by chance, then we could not infer that he can detect the sweet sample. The result, however, is just as unusual or improbable an outcome as a frequency of the same excess above the chance expectancy. In this case we are interested only in the probability of the frequency of correct choices exceeding a given value, and this is properly a one-sided or one-tailed test. A significantly small number of correct choices would have no positive bearing upon the taster's ability to detect sugar. All frequencies of choices less than the significant number of correct choices would constitute negative evidence concerning his ability. These samples could equally well have been presented in a triangular test.I n the second case (b), suppose that the tasters of a panel are given several samples each of which contains two commodities, presented as a paired-sample or triangular comparison, and are asked to indicate which of the two they prefer. If we assume that some will prefer one and some the other in about equal numbers, then a large number of selections of the one commodity over the other may indicate, on the basis of the panel's judgment, a significant quality or preference difference between the two. Since either sample may be the preferred one, the appropriate test is twosided or two-tailed. The selection of a particular commodity an unusually large number of times is just as interesting as its selection an unusually small number of times. 117

Sweetness acceptance of novices, experienced consumers and winemakers in Hunter Valley Semillon wines

“…1-3 illustrate the number of respondents who preferred the glucose spiked wine at each of the additional glucose concentrations for consumer categories 'novice', 'experienced' and 'wine makers', respectively. Using the 0.05 confidence level for paired comparison tests (n = 25, Roessler, Baker, & Amerine, 1956) the maximum level of glucose that could be added and still preferred by the novice group in comparison to the base wine was therefore determined to be 16.0 g/L for wine A and 4.0 g/L for the wine B. This infers that novices preferred wine A with up to an additional 16.0 g/L, and wine B sweetened with 4.0 g/L of glucose, compared to the corresponding base wines.…”

Threshold Values of Soluble Solids in Fruit Determined for the Fresh Fruit Market

“…The area of indecision is calculated according to Roessler et al (1956). With 100 or more replicates the area of indecision ranges from 39 to 61 % acceptance ( P sO.05).…”

Consumer rejection threshold for 1,8-cineole (eucalyptol) in Australian red wine

“…1 illustrates the proportion of respondents who preferred the reference or un-spiked sample at each experimental concentration. Using the 0.05 probability level for paired comparison tests (N = 40;Roessler, Baker, & Amerine, 1956), the CRT is calculated to be 27.5 ppb.…”