ABSTRACT
Random selection of samples is important issue. In random sampling, everyone in the sampling frame has an equal probability of being chosen. For a sample to be truly representative of the population, a random sample should be taken. There are many different random sampling systems, but one simple method is to use a random number table or a computer program to produce a random number list to select the sample. Multi-stage sampling can also be used. For example, in a study of university students in the United Kingdom, it would be difficult to obtain a complete list of all students. Cluster sampling is similar to multi-stage sampling, except that all of the subjects in the final-stage sample are investigated. It can be useful to employ stratified sampling to randomly select subjects from different strata or groups. Imagine a study designed to examine possible variations in healthcare between Asian and non-Asian patients.
