MET Sampling Flashcards
(14 cards)
Population definition
Who the study is about and who the results apply to
Who the sample is chosen from
Sample definition
People who take part in a study - the participants
What should participants be?
Representative of the population
What is a representative sample? What does this mean the results are?
Consists of a selection of typical members of the population
Generalisable - what is true of sample is true of population
What is a biased sample?
Over or under represents certain groups or characteristics
Not representative of population
Results cannot be generalised to population
What is random sampling? What is quasi-random sampling? What two random sampling techniques are there?
Process of choosing participants involves only random process
Quasi-random sampling includes stratified and systematic sampling - because the pps are obtained from a list not the full actual population
Computer method - allocate each name a number, use a randomised program to select N numbers, pps are those numers are chosen
Manual method - put each name on paper in container, choose N pieces of paper, pps are those whose names are chosen
Strengths and limitations of random sampling
Strengths - best probability of representative sample, taking choice out of researcher’s control eliminates bias
Limitations - sample could be unrepresentative of some groups by chance / random error
What is stratified sampling?
Sampling population identified, appropriate strata/groups divide sample, proportions needed for representative group identified, random sampling used to choose the appropriate N from each strata
Strata used should be ones that might affect results
What is systematic sampling?
Specify population, identify sampling population
Work out proportion of sampling population for N
Choose every nth member of the sample
Commonly done to avoid time-consuming random sampling, or awkward practical issues such as fast cars going past
What is opportunity sampling?
Use whoever is available
For example - Unis - use own students
What is volunteer sampling?
Recruit via advertisements online/public places
Volunteers come forward
Strengths and limitations of stratified sampling
Strengths - more likely to be representative
Limitations - time consuming
Strengths and limitations of systematic sampling
Strengths - more practical than random, likely to be representative
Limitations - small chance of systematic error
Strengths and limitations of opportunity and volunteer sampling
Strengths - less time consuming, no need for sampling population
Limitations - less likely to representative, especially volunteers as they are more likely to be parts of certain groups or have certain characteristics
