Research Ethics - Sampling

One of the first steps in establishing your research design will be deciding upon which group of people, the population, you wish to focus on. Subsequent to this, you will need to determine the sample of participants within this population, thus moving toward deciding upon your sampling method.

As an ethical consideration, it is vital that, in describing your sampling method, you give appropriate justification for the inclusion or exclusion of particular groups of people. There are numerous factors that may inform these criteria, such as the participant's age, socio-economic background or professional knowledge-base. Other sampling criteria may also mean that your application must be submitted to an external research ethics committee for approval. As in the case of participants who may be regarded as having diminished mental capacity, or participants selected on the basis of their employment with the NHS.

Your application to University Research Ethics Committee (UREC) must give a clear rationale for why the group of people you wish to focus on needs to be involved in your proposed research. Similarly, you must also provide reasonable grounds for justifying the exclusion of other categories of people.

This is not simply a consideration of good ethical practice, it is also a factor that will influence the quality and applicability of potential findings yielded by the research. It is vital to consider whether or not the proposed research will produce valid results if the sampling involves the exclusion of certain groups. Some useful guidance questions are provided below:

Can the sample be considered as representative of the population?
Can the decision to exclude these groups be justified?
Can the exclusion of these groups be regarded as ethical?

The Research Ethics Guideboook puts forward a useful example that further illustrates this principle:

An example: research with young children

Researchers studying childhood often sample children aged 8-17 years only. Reasons that are given to support this practice might include: children aged under 8 years do not have clear views; they are not able to express views clearly; they cannot be relied on to provide valid evidence; they are too vulnerable to be included in research studies. Yet increasingly researchers and practitioners find that young and even preverbal children provide valuable data through their talk and behaviour, and that ignoring their views can unhelpfully distort research findings, policy and practice.