Lesson 8: Sampling Techniques

Target Population The target population is the group of people the researcher is interested in studying. It is usually not possible to investigate the entire target population because it is too large, it would take too long, and it would cost too much money.

Therefore researchers need to choose a sample from the population. This sample should be representative of the target population so that the findings from the study can be generalised to the entire target population.

If the sample is not representative then it is biased and the validity of the study can be questioned. This is because the study lacks population validity.

Random Sampling This sampling technique involves every single member of the target population having an equal chance of being chosen to take part. In order to achieve this every member of the target population is identified and then a random sampling technique is applied.

This sampling technique is the most likely of all to lead to a representative sample. It is difficult to obtain because researchers must have access to every member of the target population. If a participant drops out, refuses to take part, or can not be reached then the sample becomes less random.

Opportunity Sampling This sampling technique involves using people who are readily available to the researcher. The researcher approaches people who happen to be available at the time and asks them if they are willing to take part in the research.

This is the most popular technique because it is convenient, cheap, and easy. There is a high chance that the sample will not be representative of the target population. Sometimes people feel obliged to take part in research even when they do not really want to.

Volunteer Sampling This sampling technique involves participants self-selecting themselves to take part in the research. The researcher will usually advertise for people to take part in their research.

This can be a useful way of finding people to take part in specific areas of research. A certain type of person tends to volunteer and this means that there is a very high chance that the sample obtained will be unrepresentative (volunteer bias).