Not all experiments are the same
How you design a study depends on the question you’re asking. In medicine, the most appropriate type of study depends on whether you are trying to diagnose, treat or calculate the likely outcome of a condition. For more on this, see ‘Types of medical study’.
In ecology, as in medicine, samples are taken: examining an entire population can be time-consuming and damage the environment you’re looking at. The design of the study depends on what you’re investigating. For example, to estimate the size of an animal population, researchers often use a mark–release–recapture method.
Marking and releasing a set number of individuals, then capturing another set number and counting how many individuals got caught twice gives a good indication of how many animals there are altogether. To sample plant populations, quadrats are used so that each sample comes from a speciﬁc area of ground.