What is sampling?
The method by which researchers select the participants that will be in their study
What is a sampling frame?
The list of people from which a sample is drawn, e.g. list of pupils in a school
What is a sampling method/technique?
The way in which participants are chosen, e.g. random sampling
What is a sample?
The actual group of participants that will be used in the research
What is random sampling?
Each person has an equal chance of being selected, e.g. picking names from a hat
What are some advantages of random sampling?
- Very fair as everyone has an equal chance of being selected
- Less chance of a biased sample as it is not ‘chosen’ by the researcher
What are some disadvantages of random sampling?
- Not guaranteed that all participants chosen would want to take part (lack of informed consent)
- Time consuming; putting together a sampling frame, choosing participants, re-choosing if people don’t want to take part
What is stratified random sampling?
The sampling frame is first sorted into groups/categories (e.g. gender/ethnicity), then participants are chosen randomly from within each group
What are some advantages of stratified random sampling?
- Allows the researcher to control the variables important to the research
- Makes the study more reliable and scientific
- Increases representativeness as the proportions of the sample can be made to reflect the proportions of the target population
What are some disadvantages of stratified random sampling?
- More complex and not practical as the sampling frame may not include the required information (e.g. participants’ gender)
- Time consuming; must find exact proportions of certain groups
- Not guaranteed that all participants chosen would want to take part (lack of informed consent)
What is volunteer sampling?
Where individuals come forward to take part in the research, e.g. in response to an advert
What are some advantages of volunteer sampling?
- Quick, easy, and cheap. Researchers just have to wait for replies
- Informed consent is gained easily as participants have chosen to take part
What are some disadvantages of volunteer sampling?
- Volunteer bias; only a certain kind of person will come forwards for certain studies
- May be hard to gain access to certain participants, e.g. domestic violence victims
What is opportunity sampling?
Participants are people who are both easily accessible and willing to take part
What are some advantages of opportunity sampling?
- No sample frame is needed as it is dependent on who is in the ‘right place at the right time’
- Very quick, easy, and convenient to get a sample
What are some disadvantages of opportunity sampling?
- Not everyone has an equal chance of being selected; only those who are there can be chosen
- Not representative as there is no control over who is available
What is snowball sampling?
Where one participants refers to the researcher to others. This continues until the required sample size is met
What are some advantages of snowball sampling?
- Useful way to contact people who might be difficult to find/persuade, e.g. criminals
- No sample frame needed as it is dependent on who you are referred to
What are some disadvantages of snowball sampling?
- Could be a biased sample, as participants are likely to refer people they know well/who are similar to them
- Not necessarily representative of the target population
