Why use sampling?
Identifying and counting every organism in a large or complex habitat is often impractical. Biologists can instead examine selected parts of the habitat and use those observations to estimate patterns across the wider area.
In random sampling, sampling locations are chosen randomly, commonly with a random number generator. This prevents the investigator's preferences from determining which parts of the habitat are examined.
The sampling area and number of samples need to be sufficient to provide a useful estimate for the habitat being investigated.
What can be investigated?
Random sampling can provide information about both distribution and abundance.
- Distribution concerns the pattern of locations in which a species occurs across the habitat.
- Abundance concerns how many organisms of a particular species are present.
Exam Tip: If asked why sampling positions should be random, link random selection directly to reducing bias from the investigator choosing particular sites.