What Is The Stratified Random Sampling?

While sampling helps to estimate population parameters there may be indefinable subgroups of elements within the population that may be expected to have different parameters on a variable of interest to the researcher. For example, to the human resources management director interested in assessing the extent of training that the employees in the system feel they need the entire organization will form the population for study. But the extent , quality and intensity of training desired by middle level managers, lower level managers, first line supervisors, computer analysts, clerical workers and so on will be different for each group.

Knowledge of the kinds of differences in needs that exist for the different groups will help the director to develop useful and meaningful training programs for each group in the organization. Data will therefore have to be collected in a manner that helps the assessment of needs at each subgroup level in the population. The unit of analysis then would be at the group level and the stratified random sampling process.


Stratified random sampling as its name implies, involves a process of stratification or segregation followed by random selection of subjects from each stratum.  The population is first divided into mutually exclusive groups.