Sampling Flashcards
sampling
various sampling methods a researcher can use to decided how to select pps to take part in their investigation, drawn from the population
random sampling
- each member of population is assigned a number
- random number generator chooses a number
- this member becomes a pp
random: strength
all members of the population have equal chances of being selected
no researcher bias
random: weakness
time consuming
volunteer bias (pps can refuse to take part)
unrepresentative of population
opportunity sampling
pps happen to be available at the time which the study is being carried out so are recruited conveniently
opportunity: strength
time saving
cost saving
convenient
opportunity: weakness
unrepresentative of the population
researcher bias (choose the pps who they want to select)
volunteer sampling
involves self selection: the pp offers to take part in response to an advert/when asked to
volunteer: strength
willing pps = easy, not time consuming
more likely to cooperate in the study
volunteer: weakness
volunteer bias - may attract a particular profile of a person, therefore cannot be generalised accurately
systematic sampling
predetermined system where every nth member is selected from the sampling frame
e.g. 3rd, 6th, 9th pps chosen
systematic: strength
usually fairly representative
avoids researcher bias
systematic: weakness
not truly unbiased unless a random number generator is used
time consuming
stratified sampling
- identify strata
- calculate required proportion need for each stratum based on target population
- select sample at random from each stratum using random number generator
stratified: strength
no researcher bias
representative data bc the strata are proportional, therefore accurate generalisation
