What Is The Key Features In Probability Sampling?

When each member of the population has a known probability, not necessarily equal, of its being selected in the sample, it is called probability sampling. Simple random sampling, stratified random sampling, cluster sampling are the examples of a probability sampling. A simple random sample is a sample which is selected in such a way that each possible sample of a given size has the same probability of selection. Simple random sample can be selected by usual lottery method. But if the population is large than random random number table can be used. When the population to be studied is not homogeneous with the respect to the variable or characteristics under study then it is divided into small homogeneous group called strata. Then sample is selected from these strata.