sampling Flashcards
random sampling
each member of the target population as an equal chance of being selected
you need a list of all the members of the target population
names placed into a name generator to generate random lists
opportunity sampling
involves using participants who are available and willing to take part
e.g asking people in the street who are passing
volunteer sampling
participants select themselves to take part
e.g advert in a newspaper
systematic sampling
where everything nth member of the target population is selected from a list
stratified sampling
identify the different sub groups
proportions needed for the sample to be representative is worked out
participants that make up each sub group are selected using random sampling techniques
target population
the entire population
representative = high…
external validity
to generalise results to the target population the sample must be…
representative
the 5 sampling techniques
random
opportunity
volunteer
systematic
stratified
random sampling strength
unbiased selection
the researcher has no influence over who is selected so can’t choose people who will support their hypothesis
this ENHANCES INTERNAL VALIDITY
random sampling weaknesses
impractical
its difficult and time-consuming to get a complete list of the target population. some selected participants may refuse to take part
may not be representative by chance
its still possible for the random sample to select similar people
opportunity strength
quick and easy
its convenient and saves time, effort and less costly
opportunity weakness
unrepresentative/ lacks generalisation
its drawn from a specific area so findings cannot be generalised
volunteer strengths
easy
requires minimal effort and input from the researcher so its less time-consuming
volunteer weakness
volunteer bias
asking for volunteers may attract a certain ‘profile’ of people like helpful, keen, curious. this affects how far findings can be generalised
demand characteristic
curious people
systematic strength
unbiased selection
once the system for selection has been established the researcher has no influence over who is chosen. this is an objective method
systematic weakness
its only possible if you can identify all the members of the target population and they’re willing to take part
this takes time and effort to make a complete list of the population
stratified strength
unbiased/ representative
once the target population has been sub-divided into the Strata the participants that make up the numbers are randomly selected and beyond the influence of the researcher
= generalisation of findings is possible
stratified weakness
stratification is not perfect
the identified strata cannot reflect all the way that people are different
so complete representation of the target population is not possible
