Choosing a study sample is an important step in any research project since it is rarely practical, efficient or ethical to study whole populations. The aim of all quantitative sampling approaches is to draw a representative sample from the population, so that the results of studying the sample can then be generalized back to the population. The selection of an ppropriate method depends upon the aim of the study. Sometimes less rigorous methods may be acceptable, such as incidental or quota samples, but these methods do not guarantee a representative sample. The most common approach is to use random, or probability samples. In a random sample the nature of the population is defined and all members have an equal chance of selection. Stratified random sampling and area sampling are variants of random sampling, which allow subgroups to be studied in greater detai