Nonprobability sampling

A type of sampling that relies on personal judgment somewhere in the element selection process and therefore prohibits estimating the probability that any population element will be included in the sample. The researcher can arbitrarily or consciously decide what elements to include in the sample. Nonprobability samples may yield good estimates of the population characteristics. However, they do not allow for objective evaluation of the precision of the sample results. Because there is no way of determining the probability of selecting any particular element for inclusion in the sample, the estimates obtained or not statistically projectable to the population. Commonly used Nonprobability sampling techniques include convenience sampling, judgemental sampling, Quota sampling and snowball sampling.