Efficient ascertainment schemes for maximum likelihood estimation

While well chosen sampling schemes may substantially increase efficiency of observational studies, some sampling schemes may instead decrease efficiency. Rules of thumb how to choose sampling schemes are only available for some special cases. In this paper we provide tools to compare efficiencies, and cost adjusted efficiencies, of different sampling schemes, in order to facilitate this choice. The method can be used for both categorical and continuous outcome variables. Some examples are presented, focusing on data from ascertainment sampling schemes. A Monte Carlo method is used to overcome computational issues wherever needed. The results are illustrated in graphs.