Probability sampling is a method of sampling, in which the items of the population have an equal opportunity to be selected, e.g, Simple Random Sampling, Stratified Sampling, Cluster Sampling, Systematic Sampling. Nonprobability sampling is a sampling technique wherein, it is not known which individual from the population will be selected as a sample, e.g., Convenience Sampling, Quota Sampling, Judgment or Purposive Sampling Snowball Sampling. In stratified sampling, the researcher divides the population into separate strata and draws a probability sample (often a simple random sample ) from each.