2.12 Optional: Designing and planning studies
This question is optional; for example, if you need more practice, or you are studying for the exam.
(Answers are available in Sect. A.2)
To study the progress of an imported species of beetle, a research group is studying the research question:
Is the mean number of species of beetle found on trees different between local coniferous and broad leaf forests?
Ten possible forests of each type have been found, and the research budget allows for 100 trees to be sampled. Three designs are being considered:
- A. Randomly sample 50 trees from one randomly selected coniferous forest, and 50 trees from one randomly selected broad leaf forest.
- B. Randomly sample 5 trees from ten randomly sampled coniferous forests, and 5 trees from ten randomly selected broad leaf forests.
- C. Randomly sample 10 trees from five randomly sampled coniferous forests, and 10 trees from five randomly selected broad leaf
The researchers wish to know which design they should use.
- Identify (with justification) which of these designs will be best for estimating the variation within a forest.
- Identify (with justification) which of these designs will be best for estimating the variation that exists between the forest (that is, from one forest to the next).
- Which design do you think would be best for answering the RQ? Explain your answer.
- Which design do you think would be the easiest design for data collection?