Probability sampling is based on the concept of random selection-a controlled procedure that assures that each population element is given a known nonzero chance of selection.

This section is devoted to the study of a few probability sampling designs, which are frequently used in sample selection. These include, among others, the following:

**Simple random sampling:**Simple random sampling is a procedure that gives each of the sampling units in the population an equal and known nonzero probability of being selected.**Systematic sampling:**Systematic sampling is a type of probability sampling method involving the selection of elements from an ordered sampling frame.**Stratified random sampling:**A restricted sampling design, which can be more efficient than simple random sampling, is stratified random sampling.**Cluster sampling:**Cluster sampling is a probability sampling technique where the population is divided into multiple groups or clusters.