Sampling methods in epidemiological studies help researchers gather information about a population by studying a smaller group, saving time and money. There are two types of sampling: probability (random selection) and non-probability (not all have an equal chance of being chosen). Probability sampling allows for generalizing findings, while non-probability sampling may lead to non-representative results. Examples of probability sampling include simple random, systematic, stratified, and clustered sampling. Examples of non-probability sampling include convenience and judgement sampling.