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.
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