Steps in Sample Design
When developing a sample design you need to keep the following points in mind:
- Defining the universe or population of interest is the first step in any sample design. The accuracy of the results in any study depends on how clearly the universe or population of interest is defined. The universe can be finite or infinite, depending on the number of items it contains.
- Defining the sampling unit within the population of interest is the second step in the sample design process. The sampling unit can be anything that exists within the population of interest. For example, sampling unit may be a geographical unit, or a construction unit or it may be an individual unit.
- Preparing the list of all the items within the population of interest is the next step in the sample design process. It is from this list, which is also called as source list or sampling frame, that we draw our sample. It is important to note that our sampling frame should be highly representative of the population of interest.
- Determination of sample size is the next step to follow. This is the most critical stage of the sample design process because the sample size should not be excessively large nor it should be too small. It is desired that the sample size should be optimum and it should be representative of the population and should give reliable results. Population variance, population size, parameters of interest, and budgetary constraints are some of the factors that impact the sample size.
- Deciding about the technique of sampling is the next step in sample design. There are many sampling techniques out of which the researchers has to choose the one which gives lowest sampling error, given the sample size and budgetary constraints.