In a research study it is not for all time possible to measure a whole representing a specific demographic. (Some illustrations of demographics are students who attend a specific college, people who live in a specific city, state or neighborhood, people of a certain age range and so on). As a result measurements are taken from a sample of that population. The subjects from a sample population surveyed require to be randomly chosen from a specific population of a specific demographic in order to be represented in an accurate way.
Random Sampling- in the simplest terms signifies that each subject eligible to be in the study has an equivalent chance of being chosen to be in the population under study. In this manner the researcher can be more confident that the people in their sample are representative of the whole population of interest.
Why would a researcher use another version of random sampling---stratified random sampling as opposed to the simple random sampling?