ISO 4120:2004描述了一种用于确定两种产品的样品之间是否存在感知差异或相似性的程序。该方法是强制选择过程。该方法适用于单个感官属性或几个属性中是否存在差异。 该方法在统计学上比二重奏测试更有效，但是对于表现出强烈携带和/或挥之不去的味道的产品的使用有限。 该方法即使当差异的性质是未知的（即既不确定样本之间的大小也不确定差异的方向，也不负责该差异的属性的任何指示）时也是可应用的。该方法仅适用于产品相当均匀的情况。 该方法对于a）当例如在成分，加工，包装等方面进行改变时，确定感知差异（差异的三角形测试）或不可见的差异（三角形测试相似性）处理或储存; b）或选择，培训和监督评估员

ISO 4120:2004 describes a procedure for determining whether a perceptible sensory difference or similarity exists between samples of two products. The method is a forced-choice procedure. The method applies whether a difference can exist in a single sensory attribute or in several attributes. The method is statistically more efficient than the duo-trio test, but has limited use with products that exhibit strong carryover and/or lingering flavours. The method is applicable even when the nature of the difference is unknown (i.e. it determines neither the size nor the direction of difference between samples, nor is there any indication of the attributes responsible for the difference). The method is applicable only if the products are fairly homogeneous. The method is effective for a) determining that either a perceptible difference results (triangle testing for difference), or a perceptible difference does not result (triangle testing for similarity) when, for example, a change is made in ingredients, processing, packaging, handling or storage; b) or for selecting, training and monitoring assessors.