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1.1 This test method covers a procedure for determining whether a perceptible sensory difference exists between samples of two products or to estimate the magnitude of the perceptible difference.

1.2 This test method applies whether a difference may exist in a single sensory attribute or in several.

1.3 This test method is applicable when the nature of the difference between the samples is unknown. The attribute(s) responsible for the difference are not identified.

1.4 The tetrad test is more efficient statistically than the triangle test (Test Method E1885) or the duo-trio test (Test Method E2610).

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 The test method is effective for the following test objectives:

5.2 The test method itself does not change whether the purpose of the test is to determine that the products are perceptibly different versus that the products are sufficiently similar to be used interchangeably. Only the selected values of α, β, and δ or P_d change. If the objective of the test is to determine if there is a perceptible difference between two products, then initially the products are assumed to be indistinguishable (for example, H_O: δ or P_d = 0) and the data are examined to determine if the assumption can be rejected (that is, conclude that the products are perceptively different). If the objective is to determine if the two products are sufficiently similar to be used interchangeably, then initially the products are assumed to be meaningfully different (for example, H_O: δ or P_d > the value chosen to represent a meaningful difference) and the data are examined to determine if the assumption can be rejected (that is, conclude that the samples are sufficiently similar to be used interchangeably).

5.3 The tetrad method involves the evaluation of four samples. When the products being tested cause excessive sensory fatigue, carryover, or adaptation, methods that involve the evaluation of fewer samples (same-different, triangle test, etc.) may be preferred.