A Thurstonian model for the degree of difference protocol

• We describe a Thurstonian model for the degree of difference methodology.
• The model provides an estimate of the size of the underlying difference δ and its variance.
• Categories boundaries (τ) are also estimated and can provide consumer relevant information.
• Results can be linked to other sensory methodologies with Thurstonian models.

In the degree of difference methodology (DOD), subjects are presented with pairs of samples, either identical or different, and must indicate how different the samples are using a t-point category rating scale. In this article, the Thurstonian model for the DOD assuming independent assessments is derived. The model permits the estimation of the size of the underlying difference between the products (δ), the variance of this estimate, as well as the sizes of the t − 1 τ criteria (scale boundaries on the difference perceptual distribution). This model expands further the collection of Thurstonian models already available for many discrimination, rating and ranking methodologies.