Sampling Techniques

Sampling

Is a process of selecting units, like people, organizations, or objects, from a population of interest in order to study and fairly generalize the results back to the population where the sample was taken.

Sampling technique

Is a procedure used to determine the individuals or members of a sample. It may be done using probability or non-probability techniques.

Probability sampling/random sampling

The probability of a unit from the population being selected into the sample is known.

Simple random sampling

The basic method of selecting survey units. Each unit in the population is selected with equal probability and all possible samples are equally likely to be chosen (ideal for small number of population)

Systematic random sampling

A random starting point in the population is selected and then every kth element encountered there after becomes an item.

Stratified random sampling

Divides the population into homogenous classes or groups (strata). Characteristics such as age, gender, or socio-economic status take a random sample from each strata.

Cluster sampling

Population is divided into groups. Elements within a cluster must be heterogenous. Each cluster has the same characteristics as the parent population.

Non-probability sampling

The probability of a unit from the population being selected into the sample is unknown.

Haphazard/convenience sampling

Method of collecting samples that are conveniently located around a location or internet service. Most useful for pilot testing.

Judgment/purposive sampling

Also known as subjective sampling, is a form of non-probability sampling in which researchers rely on their own judgment when choosing members of the population to participate in their study.

Quota sampling

Selection is done according to predetermined quotas. Each person gathering observations is given a specified number of elements to sample.

Snowball sampling

Method purely based on referrals and that is how a researcher is able to generate a sample. Is also called the chain-referral sampling method.