  The dynamics of tumour evolution are not well understood. In this paper we
provide a statistical framework for evaluating the molecular variation observed
in different parts of a colorectal tumour. A multi-sample version of the Ewens
Sampling Formula forms the basis for our modelling of the data, and we provide
a simulation procedure for use in obtaining reference distributions for the
statistics of interest. We also describe the large-sample asymptotics of the
joint distributions of the variation observed in different parts of the tumour.
While actual data should be evaluated with reference to the simulation
procedure, the asymptotics serve to provide theoretical guidelines, for
instance with reference to the choice of possible statistics.
