A sample base is a list of all eligible members of a population from which samples are taken. It can be considered the pool from which samples are taken. It is a statistical framework used in surveys, social surveys, marketing surveys, and different types of studies. This framework is necessary to reach an unbiased and accurate conclusion or finding, as it completely defines the population under study. It is usually not possible or even practical to make direct observations of each element of the population of interest, and a framework narrows the studied population to a manageable figure, helping researchers to draw conclusions about the entire population.
For example, a study aiming to find out how much time teenagers spend online cannot include all the teenagers in the world. Certain parameters are introduced to narrow down the population of interest. A sample base, in this case, might specify that the teenager lives in and around New York, is between 13 and 15 years old, has access to a computer at home, and attends a public school. A study conducted in this way can bring insights that apply to adolescents in general in this segment. Establishing a clear framework is critical to the success of any research or study, as a faulty framework leads to inconsistent or inaccurate findings or results.
Although the framework constrains the set from which the sample is drawn, it differs from the population of interest to some extent. For example, using the example above, the sampling frame does not include teenagers who access the web from their cell phones, who are not at home at the time of the call, or who are simply not interested in participating in surveys. Even entering the sample base does not guarantee that the person will become part of the final sample group. Samples can be taken randomly from the board where each person has a chance of being included, or in a more systematic way, say, when every tenth person on the list is selected.
There are a number of problems experienced by those designing a sampling frame that can skew the results. Missing members are a very common problem when those who need to be inside the board have been left out by accident. Duplicate members are also a big problem when a member is listed more than once. Sometimes foreign entries – people who do not represent the population of interest – can be found within the frame. Other times, instead of listed individuals, the board may contain groups. When there are errors in the sampling frame, the final sample taken is flawed, either as an unrepresentative sample of the study group or containing significant bias.