The definition of nonprobability sampling is a sampling technique that does not allow the same opportunity for each element or member of the population to be selected into the sample.
Nonprobability Sampling Techniques include: Systematic Sampling, Quota Sampling, Incidental Sampling, Purposive Sampling, Saturated Sampling, and Snowball Sampling.
1. Systematic Sampling
The definition of Systematic Sampling is a sampling technique based on the sequence of members on the population who have to be numbered, for example, members of a population consists of 100 people, all members of the population are numbered 1 to 100. The sampling can be done by taking the odd numbers only, even numbers only, or multiples of certain numbers.
2. Quota Sampling
The definition of Quota Sampling is a technique for determining a sample of the population that has certain characteristics until the desired amount of quota. For example, conducting research on Dental Caries, the determined number of samples is 500 people, if the data collection has not met the quota of 500 people, the study is deemed unfinished.
3. Incidental Sampling
Incidental sampling is a sampling technique by chance, that anyone who accidentally or incidentally meets with the researchers can be used as a sample if it is deemed that the person who happened to be found suitable as a source of data.
4. Purposive Sampling
Purposive Sampling is a sampling technique with particular consideration. For example, conducting research on the quality of the food, the sample of data source is the food expert. This sample is more suitable for Qualitative research or a research that does not generalize.
5. Saturated (Census) Sampling
Saturated sampling is a sampling technique which all members of the population are used as the sample. This is often done when the population size is relatively small, less than 30 people, or research to make generalizations with a very small error.
6. Snowball Sampling
The definition of Snowball sampling is a sampling technique that initially is a small amount, and then enlarged. Like a rolling snowball that is to be great. Many qualitative researches use purposive and snowball sampling. For example, conducting research about who the riot provocation is, it will be appropriate to use purposive sampling and snowball sampling.
