Hierarchical ascendant classification

A Hierarchical Ascendant Classification (Euclidean distance, Ward s criterion) was performed on the hedonic scores of the entire population four clusters can be distinguished (Fig. 20.12). Even if the number of consumers was low for Clusters 1 and 2, it seemed of interest to consider these drivers separately because they have separate opinions on RC3-P2. Cluster 1 differentiated the cars according to their seat, regardless of the chassis. Cluster 2 liked RC3-S3 and rejected RC3-P2. Cluster 3 differentiated the cars according to their chassis and not their seat. Finally, Cluster 4 differentiated the cars according to their chassis and then to their seat. 

Another conclusion concerns the relationships between the terms used by novices, marketing department employees and experts. A Hierarchical Ascendant Classification of the terms allows us to group terms used by each type of assessors. For instance, the term Claquance used by E2 is quite technical, but it is highly correlated with more understandable terms such as farm tractor noise or jackhammer noise. The terms Central frequencies and Middle High Frequencies are technical, but knowing that they are anti-correlated to Engine Power, used by several novices, allows us to understand how consumers can perceive this particular aspect of the idle noises. 

The simplest to nnderstand is the difficulty obtaining a useful consensus in the sensory description. As assessors nse their own vocabnlary, this consensus is mainly obtained mathematically by snch techniques as GPA and Hierarchical Ascendant Classification. Therefore, the correlation of two terms after GPA is the only clue that they can mean the same thing. Sadly, it is not sufficient. Two terms with different meanings can be highly correlated because of the products evaluated. 

Pun, T., Hochstrasser, D. F., Appel, R. D., Funk, M., Villars-Augsburger, V. and Pellegrini, C. 1988, Computerized classification of two-dimensional gel electrophoretograms by correspondence analysis and ascendant hierarchical chxstenag. Appl.Theor.Electrophor., 1 3-9... 

The US FDA provides a detailed hierarchal framework for device regulation. The primary stratification is the assignment of a device to a specific classification, of which there are currently 16 panels comprising 1700 types of devices. The assignment to a specific class depends upon the medical spedahty for which the device is intended. All of the devices so defined can then be further categorized with respect to three ascending classes ... 

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