ABSTRACT
Probability sampling occurs when every member of the population has an equal chance of being selected into the sample. Systematic random sampling is frequently selected as the sampling method when conducting research using social work case files. Stratified random sampling has two important features and is an important sampling method. Stratified random sampling reduces the error of sampling and ensures that all the values on the variable are represented proportionally. Cluster sampling is a random sampling method that is frequently used when the population is very large, it is difficult to obtain a complete list of the individuals and/or when the population is spread geographically. A combination of stratified and cluster sampling might actually be the method to obtain the most representative sample. In all studies, random samples are always preferable but due to cost, feasibility and access to respondents, non-probability sampling methods may have to be used.
