A two-level directional model for dependence in circular data

We present a likelihood-based test for clustering among sub-population mean directions for circular data. The test is based on a two-level hierarchical model with von Mises distributed variation on each level. The properties of the tests are investigated and compared to the commonly applied techniques of second-order analysis and pseudo-pooling of directions for the situation at hand. Finally we apply the technique to some previously published data sets, to determine the presence of directional clustering among the sub-populations. The Canadian Journal of Statistics xx: 1–18; 2017 © 2017 Statistical Society of Canada