Study design

4. When a researcher is discussing an experimental design with a colleague or biometrician he/she should be expected to be asked to justify reasons for his/her decisions not only on sample size but also on questions on numbers of treatments, doses etc. Thus, it would not be unreasonable to discuss the numbers of different genotypes that are proposed for comparison or different levels or types of feeding regimes. For example, the researcher might have wished to compare four genotypes but have realised that experimental constraints prevented this. The option of using two feeding regimes and four genotypes could, however, be explored. In this particular case the 3x3 experiment proved to be the most desirable arrangement, but in other situations adjustments to the initial proposal for the design can be fruitful.

5. Video 5 has been included with this case study to indicate the type of discussion that took place between the authors. It has already been shown that there are certain aspects of the experimental design and the proposed analysis that in hindsight might have been considered more thoroughly at the planning stage. We have included this video especially within this case study so that it can be used by teachers as a basis for role playing among their students to practise the art of consulting. A number of study questions have also been prepared with this in mind.