Chunk #9 — Materials and Methods — Methods of Analysis — Distances between Covariance Matrices

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Non-linear development of EEG coherence in adolescents and young adults shown by the analysis of neurophysiological trajectories and their covariance.

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In order to evaluate the range of variation within the observed covariance matrices, a permutation method was used in which each of the observed sequence of 96 covariance matrices for males and separately for females had its rows and columns permuted by the same random permutation and the maximum of the pairwise geodesic distances between the corresponding observed and permuted matrices recorded for each of 1000 permutations. The range of values for the maxima was between 9 and 10 for each sex, providing a estimate for the diameter of the set of comparable covariance matrices, in the sense of the within matrix distribution of the covariances.