Where do you even begin to count the number of organisms in a field, for example? How can quantitative data be obtained for a rocky shore? It’s not feasible to assess every single individual plant, count all the crabs you can possibly find, or estimate the abundance of all types of grass along a shingle ridge. Even if that was possible, the data would still not apply to the make up of a population, for example, at different times.
The answer is to obtain a sample. If a sample of crabs on a shore was to be taken, where would you look? In the spot where you can already see 3 of them, or in the spot where there are none? Well, in order for the sample to be representative, you must not involve yourself, as the experimenter, in the process of deciding the sample locations. That would incur experimenter bias and would render you hard-earned precious data invalid.
The sampling must be like those annoying, attention-seeking TikTok friends. It must be random. Random sampling can be carried out using quadrats. If you’re wondering what they are, look no further – they’re squares.
How would you make sure that your sampling is random? In a field, you could lay two long tapes perpendicularly to define the limits of the area where…