A.1.5—Sampling scientific data

A sample should represent the population relevant to the question. Random, systematic or stratified choices can reduce selection bias when their use is justified.

Define the population, sampling frame, sample size and inclusion rule; record non-response and avoid replacing inconvenient observations without explanation.

Sampling plants only beside a path may over-represent tolerant individuals; spread quadrats across the habitat and use a stated random rule.

A larger biased sample can be less informative than a smaller representative one.