A sampling in which every unit of the population has an equal chance of being selected in the sample, is called a simple random sampling.

This method is considered to be superior to all other methods of sampling, because,

• In this method there is no place for personal bias or prejudice for any unit of the population.
• The selection of each unit of sample is done independently, i.e., the selection of any unit does not depend upon the selection of any other unit.
• Which unit of the population will be selected in the sample is not decided in advance.

In this method the selection of sample units being done randomly, it is called simple random sample, which appropriately represents the population. The data of the sample units selected by this method gives reliable estimates of the population values. When the size of the population is large and the variation among the units of the population for any characteristics is more then the sample obtained by this method cannot give the reliable results.