Sampling techniques Flashcards
What is Sampling?
Sampling means selecting the group that you will actually collect data from in your research.
What are participants?
People who take part in the research.
It is important to use suitable participants in a study
What is the target population?
The target population is the group of people from whom the sample is drawn.
Why do we use sampling techniques?
It is impossible to study every single person in a target population so we use sampling techniques to select a sample or sub-group of the population that is likely to be representative of the entire target population that we are interested in.
If the sample we select is going to represent the target population then we need to make sure that the people in it are similar to the other members of the target population.
Why must samples be representative?
If your sample is representative, you can then generalise the results of the study to the wider population
What are the different sampling techniques?
(there are 6 of them)
Random
Systematic
Stratified
Snowball
Opportunity
Self-selected
What is random sampling?
Everyone in the entire target population has an equal chance of being selected.
This is similar to the national lottery.
Random samples require a way of naming or numbering the target population and then using some type of raffle method to choose those who will make up the sample.
Give an advantage of random sampling?
The advantages are that your sample will represent the target population and eliminate sampling bias
Give a disadvantage of random sampling?
it is very difficult to achieve (due to: time, effort and money).
What is systematic sampling?
Systematic sampling is a probability sampling method where researchers select members of the population at a regular interval – for example, by selecting every 15th person on a list of the population.
Give an advantage of systematic sampling?
It reduces the potential for bias
It is simple and convenient to use.
Give a disadvantage of systematic sampling?
Patterns Can Be Predicted
Unequal Selection is Possible
What is Stratified sampling?
Classifying the target population into categories, then choosing a sample that is in the same proportion as the population
Whats an advantage of stratified sampling?
More cost-effective
Prevents sample bias
More accurate data
What’s a disadvantage of stratified sampling?
Difficult data analysis
Requires more planning
Lacks versatility (only works for surveys)
What is snowball sampling?
Snowball sampling can be used if your population is not easy to contact.
You may ask a participant who fits your target population to tell their friends about the study and ask them to get in touch with you, when youll ask them to take the survey as well.
Whats an advantage of snowball sampling?
Cost effective
Gathers participants quickly
Give some disadvantages of the snowball sampling
Sample may not be representative of the entire target population. The researcher has no idea of the true distribution of the population and of the sample.
Sampling bias could occur because initial subjects tend to nominate people that they know well, who may have similar traits and charcteristics to the researcher, so the sample that the researcher will obtain is only a small subgroup of the entire population.
What is opportunity sampling?
Uses people from target population available at the time and willing to take part.
It is based on convenience.
An opportunity sample is obtained by asking members of the population of interest if they would take part in your research. An example would be selecting a sample of students in the common room.
Whats an advantage of opportunity sampling?
This is a quick and easy way of choosing participants
Whats a disadvantage of opportunity sampling?
sample population may not be representative of the target population, and could be biased
Whats Self Selected Sampling?
Self selected sampling (or volunteer sampling) consists of participants becoming part of a study because they volunteer when asked or in response to an advert.
Give an advantage of Self Selected Sampling
it is quick and relatively easy to do.
It can also reach a wide variety of participants.
Give a disadvantage of Self Selected Sampling?
They are self selected, so sample may not be representative of the entire target population.
How many recruits do I need?
This depends on several factors; the size of the target population is important. If the target population is very large (e.g. all 4-6 yr olds in Britain) then you need a fairly large sample in order to be representative.
If the target population is much smaller, then the sample can be smaller but still be representative.
What is a sample?
A sample is a subset of individuals from a larger population.
