ISO 5495:2005描述了一种程序，用于确定两种产品样品之间是否存在与感官属性强度有关的可感知感官差异或相似性。该测试有时也称为方向差测试或2-AFC测试（替代强制选择）。事实上，配对比较测试是两种选择之间的强制选择测试。 该方法适用于单个感官属性或多个感官属性中是否存在差异，这意味着它能够确定是否存在与给定属性有关的可感知差异，以及差异方向的说明，但它不会给出该差异程度的任何指示。所研究的属性没有差异并不意味着这两种产品之间不存在任何差异。 该方法仅适用于产品相对同质的情况。 该方法是有效的（1）用于确定是否存在可感知差异（配对差异测试），或是否不存在可感知差异（配对相似性测试），例如，当对成分、加工、包装、处理或储存操作进行修改时，或（2）用于选择、培训和监控评估人员。 在进行试验之前，有必要了解:，测试是单侧测试（测试主管事先知道差异的方向，替代假设对应于预期方向上存在差异）还是双侧测试（测试主管对差异的方向没有任何先验知识，替代假设对应于在一个方向或另一个方向上存在差异）。

ISO 5495:2005 describes a procedure for determining whether there exists a perceptible sensory difference or a similarity between samples of two products concerning the intensity of a sensory attribute. This test is sometimes also referred to as a directional difference test or a 2-AFC test (Alternative Forced Choice). In fact, the paired comparison test is a forced choice test between two alternatives. The method is applicable whether a difference exists in a single sensory attribute or in several, which means that it enables determination of whether there exists a perceptible difference concerning a given attribute, and the specification of the direction of difference, but it does not give any indication of the extent of that difference. The absence of difference for the attribute under study does not signify that there does not exist any difference between the two products. This method is only applicable if the products are relatively homogeneous. The method is effective (1) for determining whether a perceptible difference exists (paired difference test), or whether no perceptible difference exists (paired similarity test) when, for example, modifications are made to ingredients, processing, packaging, handling or storage operations, or (2) for selecting, training and monitoring assessors. It is necessary to know, prior to carrying out the test, whether the test is a one-sided test (the test supervisor knows a priori the direction of the difference, and the alternative hypothesis corresponds to the existence of a difference in the expected direction) or a two-sided test (the test supervisor does not have any a priori knowledge concerning the direction of the difference, and the alternative hypothesis corresponds to the existence of a difference in one direction or the other).