Significance and Use
5.1 The paired preference test determines whether or not there is a preference for one product over another product among a specific target population. Knowledge of consumer segments, brand loyalties, the range of product offerings in the marketplace, and the decision risk must be understood when planning a paired preference test.
5.2 The paired preference method is commonly used in tests with one or more of the following objectives: (1) to establish superiority in preference versus the competition for advertising claims support; (2) to establish the preference of a new product for launch versus a competitor's product; ( 3) to establish the preference of a reformulated product in a product improvement or product modification project (for example, process change or ingredient change); and (4) to establish the preference of a cost improved product versus the current formulation in a cost savings project. Selected values of Pmax, α, and β will change with all four types of test objectives. These should be selected prior to determination of N.
5.2.1 Preference versus Competition or Launching a New Product versus Competition—Select a Pmax to represent what you expect a reasonable preference split to be. The main risk to avoid is to wrongly claim your product is preferred over the competitors. Thus, low values of α are selected, for example, 0.05, 0.01, or 0.001. The desired outcome of this test is to reject the null hypothesis. The alternative hypothesis is one sided: A new or improved product (A) is preferred over the competitor’s product (B). The test is one-sided. The value of β will be determined by the sample size chosen and the size of the preference in the consumer segment selected for the test. Selection of the appropriate number of respondents is determined by Pmax, α, and β, as well as the market segment that must be included in the test (for issues specific to conducting a paired preference test for an advertising claim, refer to Guide E1958).
5.2.2 Cost Reduction or Reformulation of an Existing Product—When parity preference is the desired test outcome, values of α are increased and values of β are decreased. For example, if a product is developed which represents a significant cost savings over the current formulation and there is concern over alienation of current users, α might be selected at 0.20 and β might be selected at 0.01. Parity testing can be either one-or two-sided depending on the action standards of the test. The test is one-sided if the action standard is that the product must be parity or better. The test is two-sided if the action standard is parity only. The number of respondents chosen must reflect the risk of replacing the current product with the cost-reduced product.
5.3 A test result of superiority or parity does not ensure that the test conclusion is correct. An incorrect test result can be obtained when the sample of respondents is selected in a way that does not reflect the true preference in the population of interest, or when the number of respondents is too small to correctly reflect the preference status of the two products among the target consumer group. Careful selection of Pmax, α, and β and an appropriate selection of respondents is needed to minimize the risk of drawing an incorrect conclusion in forced-choice paired preference testing.
Scope
1.1 This document covers a procedure for determining preference between two products using either a two-alternative forced-choice task, or with the option of choosing no preference. Preference testing is a type of hedonic testing.
1.2 A paired preference test determines whether there is a statistically significant preference between two products for a given population of respondents. The target population must be carefully considered.
1.3 This method establishes preference in a single evaluation context. Replicated tests will not be covered within the scope of this document.
1.4 Paired preference testing can address overall preference or preference for a specified sensory attribute.
1.6 This method does not address whether or not two samples are perceived as different. Refer to Test Method E2164 for directional difference test.
1.7 A paired preference test is a simple task for respondents, and can be used with populations that have minimal reading or comprehension skills, or both.
1.8 Preference is not an intrinsic attribute of the product, such as hue is, but is a subjective measure relating to respondents' affective or hedonic response. It differs from paired comparison testing which measures objective characteristics of the product. Preference results are always dependent on the population sampled.
1.9 This standard does not purport to address all of the safety problems associated with its use, when testing includes hazardous materials, operations, or equipment. It is the responsibility of the user of this standard to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.
