sampling Flashcards
population and sample
population - large group of individuals that he researcher is interested in studying often called target population
sample that is drawn ideally needs to be representative of the target population so that generalisation of findings becomes possible
vast majority of samples contain a degree of bias
random sample
all members of the target population have an equal chance of being selected
obtain a complete list of all members of the target population
all the names on the list are assigned a number
actual sample is selected through the use of the lottery method such as randomly picking a number
strenght of random sampling
unbiased
confounding variables and extraneous variables should be quality divided between the groups enhancing internal validity
limitation of random sampling
difficult and time consuming to conduct
complete list of target of target population may be difficult to obtain
may end up with a sample that’s unrepresentative
systematic sampling
every nth number of the target population is selected
sampling frame is produced which is a list of people in the target population organised for example in alphabetical order
strength of systematic sampling
sampling method is objective
researcher has no influence over who is chosen
limitation of systematic sampling
is time consuming and participants may refuse to take part
stratified sampling
composition of the sample reflects the proportions of people in certain subgroups (strata) within the target population
researcher first identifies the different strat that make up the population
proportions needed for the sample to be representative are worked out
particpants that make up each stratum are selected using random sampling
strenght of stratified sample
produces a representative sample because it is designed to accurately reflect the composition of the population
generlatistipn of findings cecomes possible
limitation of stratified sampling
identifies strata cannot reflect all the ways that people are different
complete representation of the target population is not possible
opportunity sample
select anyone who happens to be willing and available
simply takes the chance to ask whoever is around at the time of their study
strength of opportunity sampling
convenient
less costly in terms of money and time as you don’t need to obtain a target population
no need to divide their population into different strata as there is stratified sampling
limitation of opportunity sampling
opportunity samples suffer from two forms of bias
sample is unrepresentative of the target population as it is drawn from a very specific area
findings annoy be generalised to the target population
researcher has complete control over the selection of participants and for instance may avoid people they do not like the look of - researcher bias
volunteer sampling
particpants selecting themselves to be part of the sample
strenght of volunteer sample
easy to collect
requires minimal input from the researcher
less time consuming than other forms of sampling
ends up with particpants who are more engaged