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AS 2542.2.1-2007 pdf free download
AS 2542.2.1-2007 pdf free download.Sensory analysis Part 2.1 : Specific methods-Paired comparison test.
5.8 The assessors shall be told whether or not they have to follow a special protocol in order to assess the products (e.g. whether or not to swallow the samples for a taste test, or carry out a specific gesture for a tactile test) or whether they are free to do as they please. In this latter case, they should be requested to proceed in the same manner for all the samples.
5.9 During the test sessions, avoid giving information about product identity, expected treatment effects or individual performance until all tests are completed.
All assessors should possess the same level of qualification, this level being chosen on the basis of the test objective (see ISO 8586-1 and ISO 8586-2). Experience and familiarity with the product can increase the performance of an assessor and can consequently increase the likelihood of finding a significant difference. Monitoring the performance of assessors over time may prove to be useful for increased sensitivity.
All assessors shall be familiar with the mechanisms of the paired test (the scoresheet. the task and the evaluation procedure). In addition, assessors shall be capable of recognising the sensory attribute on which the test is based. This attribute shall be defined verbally, by means of a reference substance or by presenting a few samples having different levels of intensity for the attribute under examination.
6.2 Number of assessors
Choose the number of assessors so as to obtain the level of sensitivity required for the test (see Table A.4 for a one-sided test and Table A.5 for a two-sided test). The use of a large number of assessors increases the likelihood of detecting small differences between the products. However, in practice, the number of assessors is often determined by material conditions (e.g. duration of the experiment, number of available assessors, quantity of product). When conducting a difference test, the number of assessors is typically approximately 24 to 30. When conducting a similarity test, about twice as many assessors (i.e. approximately 60) are required for equivalent sensitivity. When testing for similarity, evaluations should not be replicated by the same assessors. For a difference test, replications may be considered but should still be avoided whenever possible. However, if replicate evaluations are required in order to produce a sufficient total number of evaluations, every effort should be made to have each assessor perform the same number of replicate evaluations. For example, if only 10 assessors are available, have each assessor perform three paired tests in order to obtain a total of 30 evaluations.
NOTE Analysing three evaluations performed by 10 assessors as 30 independent evaluations is not valid when testing for similarity using Table A.3. However, the difference test using Tables A. I and A,2 is valid even when replicate evaluations are performed (5J, 1I. Some recent publications 111, ) on replicated discrimination tests suggest alternative approaches for analysing replicated evaluations.AS 2542.2.1-2007 pdf free download.
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