When the units of a sample are chosen so that each unit in the population does not have a calculable non-zero probability of being selected in the sample, this is called Non-Probability Sampling. Also, Non-probability sampling is a sampling technique where the samples are gathered in a process that does not give all the individuals in the population equal chances of being selected. In contrast with probability sampling, non-probability sample is not a product of a randomized selection processes. Subjects in a non-probability sample are usually selected on the basis of their accessibility or by the purposive personal judgment of the researcher.
Scope of Non-Probability Sampling:
•This type of sampling can be used when demonstrating that a particular trait exists in the population. •It can also be used when the researcher aims to do a qualitative, pilot or exploratory study. •It can be used when randomization is impossible like when the population is almost limitless. •It can be used when the research does not aim to generate results that will be used to create generalizations pertaining to the entire population. •It is also useful when the researcher has limited budget, time and workforce. •This technique can also be used in an initial study which will be carried out again using a randomized, probability sampling.
Advantages of Non-Probability Sampling:
•Used when sampling frame is not available
•Useful when population is so widely dispersed that cluster sampling would not be efficient •Often used in exploratory studies, e.g. for hypothesis generation •Some research not interested in working out what proportion of population gives a particular response but rather in obtaining an idea of the range of responses on ideas that people have.
Types of Non-Probability Sampling:
There are five types of Non-Probability Sampling, they are: 1.Convenience Sampling.