The Bayesian approach to the prediction of particle type given measurements of particle location is explored, using a parametric model whose prior is based on the transformation group. Two types of particle are considered, and locations are expressed in terms of a single spatial coordinate. Several cases corresponding to different states of prior knowledge are evaluated, including the effect of measurement uncertainty. Comparisons are made to nearest neighbor classification and kernel density estimation. How one can evaluate the reliability of the prediction solely from the available data is discussed.