*3.1. Filter Methods*

Analysis of variance (ANOVA) is a parametric statistical filter method to determine significant differences between group means. Related to ANOVA is the non-parametric Mann-Whitney U-test, and the Kruskal–Wallis test which extends the Mann–Whitney U-test for more than two groups [45]. Following initial dimensionality reduction by one of these methods a secondary feature selection step to further reduce the number of selected features is used, such as Linear Discriminant Analysis (LDA) [35,52], classification and regression trees (CART) [32,37,39], or the manual selection of known influential bands [8,45,46]. This secondary selection step found important bands in the VIS and SWIR, with a reduced selection of NIR bands [39,52]. However, the reverse was found by [32] where CART secondary selection was restricted to NIR wavelengths. The remainder of the studies manually selected bands that differentiated the greatest number of species pairs [8], or selected known influential bands from the wavelengths that demonstrated high levels of pairwise group variance [45,46].
