Although simple random samplings are a common research method, they are expensive to use, extremely time consuming and difficult to organize. A simple random sampling requires a complete list of all members of the target population so that the sample is a real representation of the larger group. Each individual in the population has the same chance of becoming part of the sample. All possible combinations of the sample are equally likely to occur, as well.
Depending upon the geographic spread of the population, simple random sampling is sometimes expensive and, on occasion, simply too massive. If collecting data from the sample takes too long because of the size, the data may become outdated before the study is completed. In addition, the membership of a population or sample varies if too much time passes. It is extremely difficult to conduct personal interviews as part of the simple random sampling method because the number of participants is often just too large. This means that the type of data collected is limited to what can be collected efficiently. Even though the sampling is intended to represent the entire population, small minority populations are sometimes missed because enough members simply are not selected when the sample is chosen by lottery.