Applications: assessment and conclusions

The analyses of Chaps. 6–12 were intended to illustrate how and to what extent canonical analysis can contribute towards the attainment of ecological goals. More specifically, the analyses were directed towards revealing something of the varied opportunities offered by canonical analysis in analyzing ecological data; the flexibility of canonical analysis which results under specialization of the variables; and the existence of connections between canonical analysis and other statistical methods widely used in ecology. The present chapter addresses the question of the worth of the analyses in ecological terms. In evaluating the analyses, appeal will be made to information outside the analyses themselves as well as to internal, data-based criteria. Scaling methods generally, of which canonical analysis is one, are difficult to evaluate except by reference to existing substantive knowledge — in other words, that is, by reference to information external to a particular analysis. This process is sometimes known as validation and has the general goal of adding conviction to the results of an analysis. The most convincing evidence for the validity of a result is that it leads to further insight. External assessment will be guided and informed by the use of internal, data-based indices. In particular, reliance will be placed on indices of variance accounted for. However, neither external knowledge nor explained variance offer entirely satisfactory means of evaluating an analysis. As the true relationships of interest are rarely known with certainty, in seeking external support reliance has inevitably to be placed on preconceived ideas as to what the true relationships might be.