Optimal determination of most probable numbers.

Choosing the design of a dilution series experiment on the basis of availability of most probable number tables can result in a non-optimal design. Similarly, certain tables and/or rules for declaring dilution series results 'improbable' do not always give optimal decisions. Further, tables of most probable number confidence intervals are not all based on the same assumptions and give different intervals--which should be used? The aim of this article is to draw microbiologists' attention to these issues and to suggest practical solutions.