Study questions

1. Suppose that the researcher really wished to assess four genotypes but was constrained to having no more than 80 goats on experiment. Meet with another student to discuss the problem and prepare a discussion in class with one student playing the role of researcher and the other as biometrician.

2. A few extra goats were purchased as replacements for each genotype. Discuss why it might be useful to have these extra goats and when such goats might be used to substitute other goats during the course of the study. How would the researcher decide which 24 goats from the total number available for each genotype to allocate to the experiment?

3. The layout of a typical animal experiment is illustrated in one of the photographs. It can be seen that pens are situated in parallel rows. As explained in the case study it is sometimes a good idea to form blocks of goats so that each genotype x feeding regime is included within each block in order to account for temperature or air movement variation across the building. Include a sentence or two within the protocol to describe how this should be done for the experiment described and modify the structure of the analysis of variance accordingly.

4. Often in animal experiments researchers elect to order animals according to their body weights and 'block them' into groups (in this case groups of nine) and then assign them at random to treatment from within each group. What might be the advantage of this and why do you think that the researchers decided not do so in this study.