So, you are using laboratory
animals for your experiment. The first thing you need to do is to carry out a power analysis, in order to work out how many animals you will need for your study.
How are you allocating
animals to treatment groups? In other words, are you randomly placing each
animal into a group (e.g., control or treatment) or is this being determined in
another way (e.g., wild-type vs. mutant)?