Define Stratified Random Sampling
Stratified Random Sampling is the elements in the population are first divided into groups called strata, such that each element in the population belongs to one and only one stratum. The basis for forming the strata, such as department, location, age, industry type, and so on, is at the discretion of the designer of the sample. The best results are obtained when the elements within each stratum are as much alike as possible. If strata are homogeneous, the stratified random sampling procedure provides results just as precise as those of SRS.