In non-probability sampling, in contrast with its probability analogue, some elements in the population have a zero probability of getting selected or unknown. Because of this, the technique’s representativeness becomes doubtful, and the margin of error becomes uncertain.
Convenience Sampling
As the name suggests, convener sampling picks the samples that are easily accessible. For example, a researcher working on the relationship between coffee drinking and body mass does a survey among her close friends and relatives!
Snowball Sampling
In snowball sampling, initially, a small group of participants are recruited (as per convenience!). The sample is extended by asking the first group to provide their contacts for new participants. And it goes on.
Purposive Sampling
In purposive sampling, the researcher uses her judgment to select the participants. A typical example is seeking expert opinion.
Quota Sampling
It is similar to the strata sampling technique; however, the elements are selected based on convenience sampling.
