Sampling Flashcards
What is opportunity sampling?
Consists of taking the sample from people who are available at the time the study is carried out and fit the criteria you are looking for.
Outline strengths of opportunity sampling.
Ease of formation: uses people who are readily available.
Natural experiments: has to be used as the research cannot recruit - the research has no control over who is studied. E.g. Hodges and Tizard’s effect of institutes.
Outline weaknesses of opportunity sampling.
Unrepresentative: cannot be generalised to target populations (e.g. data was collected during town on a weekday, it is unlikely to include those who go to college/ work full time).
What is random sampling?
A sample in which every member of the population has an equal chance of being chosen.
This involves identifying everyone in the target population and then selecting the number of participants you need in a way that gives everyone in the population an equal chance of being picked.
Outline strengths of random sampling.
Unbiased selection: therefore more likely to be representative.
Generalisation: if representative then you’re results can be generalised to the target population.
What is stratified sampling?
Involves classifying the population into categories and then choosing a sample which consists of participants from each category in the same proportions as they are in the population.
Outline weaknesses of random sampling.
Impractical: difficult to achieve; difficult to get full details of target population – not all will be available, some may not want to take part.
Not always representative: does not guarantee an unbiased sample. E.g. all females could be randomly selected.
Outline strengths of stratified sampling.
Unbiased selection: therefore more likely to be representative.
Generalisation: if representative then your results can be generalised to the target population.
Outline weaknesses of stratified sampling.
Knowledge of populations characteristics required or may not be available.
Time consuming.
What is volunteer sampling?
Self-selected sampling which consists of participants becoming part of a study because they volunteer when asked or in response to an advert.
Outline strengths of volunteer sampling.
Ease of formation: creating sample requires little effort – placing an advert.
Less chance of the “screw you” phenomenon – PPs are eager to take part – less chance of deliberate sabotage.
Outline weaknesses of volunteer sampling.
Unrepresentative: volunteers tend to be a certain “type” of person, thus unrepresentative – not generalisable to target populations.
Demand characteristics: volunteers are eager to please – increases chances of DCs.
