Free sorting task

Several variants of the free sorting task have been developed for specific objectives. Since they differ in terms of the instructions given to the subjects and the type of collected data, they can be considered as separate procedures. 

The multiple sorting task and the taxonomic sorting task are variants that allow the assessment of a more refined evaluation of the dissimilarities between stimuli at the subject level than the (single) free sorting task. 

In free sorting task, let us consider the matrix A = (5y) of global dissimilarities between products. As stated above, the dissimilarity 5 between products i and j (i, j = 1,. .., n) is equal to the number of subjects who did not set these two products in the same group. Let us denote by X the representation space of dimension k (say). We suppose for the time being that the parameter k is fixed. We denote by di/X) the Euclidean distance between products i and j obtained from the coordinates of products i and j in the representation space, X. The optimal representation space is obtained by minimizing a criterion called Stress (Kruskal, 1964) ... 

We will also outline the representation of the products by means of an additive tree. Indeed, this is an appealing concept, which has been used in several studies related to the free sorting task. 

Let us consider two partitions of the same n products. For instance, these could be the partitions of the same stimuli operated by two subjects in the course of a free sorting task. The Rand index (Rand, 1971) is defined by ... 

The aim of this study is to better understand the consumers representations and perceptions of car body styles, and assess the effect of the physical parameters of cars on the consumers perceptions. For this purpose, we have developed a methodological approach using experimental designs and free sorting task procedure. 

Figine 7.7 shows the distribution of the number of groups that the consumers set up in the coinse of the free sorting task. It can be seen that this number ranges between 2 and 17, with an average number of seven groups with a relatively high variability (StD = 2.9). 

Free sorting task can also be used to assess the respective importance of design parameters in an optimization process of product development. In this context, the designer can focus on parameters that define the different categories of the products inferred from the consumers perceptions. 

Courcoux, R, Faye, P. and Qannari, E. M. (2014). Determination of the consensus partition and cluster analysis of subjects in a free sorting task experiment. Food Quality and Preference, 32, 107-112. 

Parizet, E. and Koehl, V. (2012). Application of free sorting tasks to sound quality experiment. Applied Acoustics, 73, 61-65. 

Qannari, E. M., Courconx, P., Taylor, Y., Buck, D. and Greenhoff, K. (2010). Statistical issues relating to hierarchical free sorting task. 10th Sensometric Meeting Past, Present, Euture, 25-28 July 2010, Rotterdam, The Netherlands. 

In a first step, data from the continuous scales can be coded from 0 for same taste , to 10 for totally different taste . By analogy with the free sorting task (see the... 

If this is not the case, but if you already have knowledge or expertise about the sensory space derived from your product set, use it You can, for example, process a classification of your products on the basis of a quantitative analysis or a free sorting task. After classification, you can choose a prototype of each cluster as the best representative of this cluster (the closest to the barycentre, for example). 

Tasks involving ranking or sorting products according to their sensory proximity are often proposed as fast and costless methods to describe the structure of a product space or even to describe the sensory properties of products (napping task, free sorting task). To our knowledge, no study has until now been carried out to assess... 

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