The statistical analysis of autoradiographs I. Grain count distributions over uniformly labelled sources

Autoradiographs have been prepared of sections of tritiated poly-n-butyl methacrylate ('tritiated polymer'). Repeated visual grain counts over the sections showed good agreement with predictions from a Poisson distribution, as did similar counts of background from around the sections. Photometric measurements of grain density from the same material could also be analysed in terms of a Poisson distribution. The processes of autoradiography and grain counting whether visual or photometric, do not necessarily introduce any added variance to that attributable to the randomness of radioactive disintegration.