Performance indices and isotropic scaling factors in sensory profiling

A new procedure for the determination of the isotropic scaling factors in G eneralised Procrustes Analysis is discussed. A noteworthy feature of this p rocedure is that each isotropic scaling factor is shown to be the product o f a standardisation scalar which adjusts for the differences in range of sc oring among assessors, and a performance index. An overall performance inde x for the whole panel is also discussed. The performance indices can be use ful in improving the performance of the panel by pointing out whether furth er training is required for the whole panel or for some specific assessors. Once the isotropic scaling factors are determined, it is possible to deriv e a group average configuration using one of several algorithms proposed in the statistical literature which aim at matching a set of configurations b y means of rotations. A data set is analysed and a simulation study is unde rtaken in order to demonstrate the method, and the outcomes are compared to those obtained by means of Gower's algorithm for Generalised Procrustes An alysis. (C) 1999 Elsevier Science Ltd. All rights reserved.