research methods- sampling Flashcards
population
large group of people that a researcher is interested in studying
-i.e. college students from the north west
sample
-the smaller group of a population thats collected (as its not often possible to include all members of the population in the study)
generalisation
sample is drawn should be representative of the population so generalisations can be made
bias
most samples are biased in that certain groups (e.g. men, students, professionals etc) may be over- or under-represented
what is random sampling?
every person in the target population has an equal chance of being selected
how does random sampling work?
lottery method
-all members of target population assigned a no. and placed in a hat or computer/phone randomiser is used
evaluation of random sampling
+potentially unbiased
-time-consuming and may not work
ao3 of random sampling: potentially unbiased
-means CVs/EVs controlled
-enhances internal validity
ao3 of random sampling: time-consuming and may not work
-complete list of population is hard to get
-also some p’s may refuse to take part
what is systematic sampling?
p’s are selected using a sampling frame e.g. list in alphabetical order
how does systematic sampling work?
every nth person is selected from a list of the target population
evaluation of systematic sampling
+unbiased
-time and effort
ao3 of systematic sampling: unbiased
-first item is usually selected at random
-objective method
ao3 of systematic sampling: time and effort
-complete list of population is required
-may as well use random sampling
what’s stratified sampling?
sample reflects proportions of people in certain subgroups (strata) within a population
how does stratified sampling work?
-subgroups (stravas) are identified, e.g. gender or age groups. relative percentages of the subgroups in the population are reflected in the sample
evaluation of stratified sample
+representative method
-stratification is not perfect
ao3 of stratified sample: representative method
-characteristics of the target population are represented
-generalisability more likely than other methods
ao3 of systematic sampling: stratification not perfect
-strata cannot reflect all the ways in which people are different
-complete representation is not possible
what is opportunity sampling?
-people who are simply most available, i.e. the ones who are nearest/easiest to obtain
how does opportunity sampling work?
ask people nearby, e.g. ask the students in your class to take part or ask people who walk past you at a shopping centre
evaluation of opportunity sampling
+quick method
-inevitably biased
ao3 of opportunity sampling: quick method
-opportunity sampling id convenient bc u can make use of the people who are closest
-makes it cheaper and one of the most popular sampling methods
ao3 of opportunity sampling: inevitably biased
-sample is unrepresentative of the target population as its drawn from one very specific area, such as one street in town
-findings cannot be generalised
what is volunteer sampling?
-participants select themselves, self-selecting
how does volunteer sampling work?
-advertise
-for example place an advert in a newspaper or ask people to put up their hand to volunteer
evaluation of volunteer sampling
+p’s are willing
-volunteer bias
ao3 of volunteer sampling: participants are willing
-p’s have selected themselves and know how much time and effort is involved
-likely to engage more than people stopped in the street
ao3 of volunteer sampling: volunteer bias
-p’s may share certain traits, e.g. want to be helpful
-respond to cues and generalisation limited
