# Total Population Sampling

Total population sampling is a type of purposive sampling where the whole population of interest (i.e., a group whose members all share a given characteristic) is studied.

It is most practical when the total population is of manageable size, such as a well-defined subgroup of a larger population. For instance, total population sampling would be a good way to conduct a survey meant to get the opinions of third grade schoolgirls from a local elementary school; all that would be required is to survey each girl in every third grade classroom.

In practice, total population sampling is done when the target group is small and set apart by an unusual and well-defined characteristic. This might be something like US city mayors that have immigrant backgrounds, or college presidents with more than five children, or family members of those suffering from a rare disease that affects one in a million.

## Steps in Total Population Sampling

1. Completely define the population and the characteristic or characteristics which set it apart.
2. Create a list of the population.
3. Collect relevant data from all members on the list.

Gleaning information from the total population often gives deeper insights into a target population than partial samples would be capable of. It has the potential to allow a researcher to paint a much more complete picture, and greatly reduces guesswork.

It also eliminates the risk of biased sample selection that is often encountered in would-be random study samples.

But since sampling a total population means you need to first draw up a list of the whole population, it is often not easy. That first list is, in many cases, very difficult or almost impossible to get. This may be the most time-consuming part of a study; and any errors or omissions can flaw the whole study.

Another disadvantage is the difficulty, even after the complete list is made, in ensuring the data collected really is complete. In the case of a survey, non-response can badly skew results if the non-respondents are not random members of the population; if they share certain characteristics not shared by others.

## References

Laerd Dissertation, Lund Research Ltd. Total Population Sampling.