I have a question regarding an area that is often skimmed over in sample size calculations. How do sample units relate to replicates in the calculation of the sample size estimates.
For example, say I designed an experiment looking at how a particular treatment may impact fish. I have a control group with 5 independent tanks each containing 30 fish, and an equal amount of tanks and fish for the treatment group. Is my total sample size = 10 (number of tanks) or 300 (number of fish)? If the former, how do I incorporate the number of fish per tank into a sample size calculations?