Sampling techniques Flashcards
Define random sampling.
A sample in which all members of the target population have an equal chance of being selected to participate in research.
What are the strengths of random sampling?
As the researcher has no control over who is selected, investigator bias is avoided.
What are the limitations of random sampling?
Although based on sound laws of mathematical probability that predict that by chance samples should be representative, there is still a possibility that they will not be, thus limiting generalisability.
Define systematic sampling.
A mathematical selection of participants when the population size is divided by the sample size to dictate which participants are selected for the sample - every nth name from the sampling frame.
Define stratified sampling
Aims to ensure that the key characteristics of the population are represented in the same proportion in the sample.
What are the strengths of stratified sampling?
By guaranteeing that all key characteristics are present in the sample, it not only avoids investigator bias but is representative so can be generalised.
What are the limitations of stratified sampling?
If all the key features of the population are not identified, then the sample may not be representative.
Define opportunity sampling.
A sample that consists of participants who were selected because of their availability.
What are the strengths of opportunity sampling?
Since the selections of participants is very straightforward, it is less time-consuming than other techniques.
What are the limitations of opportunity sampling?
The researcher may consciously or subconsciously show bias in sample selections thus limiting generalisability.
Define volunteer sampling.
A sample where the are participants self-selected.
What are the strengths of volunteer sampling?
Since the selection of participants is very straightforward it is less time-consuming than other techniques.
What are the limitations of volunteer sampling?
Sample bias is likely as only certain types of people are motivated to volunteer for research thus limiting generalisability.
What are the strengths of systematic sampling?
The only input the researcher has is deciding the sample size, therefore it avoids investigator bias.
What are the limitations of systematic sampling?
As with a random sample, there is still the possibility that the sample will not be representative thus limiting generalisability.
