Random Sampling – a sampling technique where each sample of its size has an equal chance of being selected.

Stratified Sampling – a sampling technique whereby the population is divided into strata according to given criteria and the sample that is chosen preserves the strata proportions.

Systematic Sampling – a sampling technique where the sampling starting point is chosen randomly and the rest of the sample is chosen periodically thereafter.

Quota Sampling – similar to stratified sampling but researchers may select the units they require from the given strata.

Opportunity Sampling – is obtained when members from a given population are willing to participate in the investigation, such as a survey.