opportunity
- taking the sample from people who are available at the time the study is carried out and fit the criteria your are looking for
+ of opportunity
cheap + quick (not time consuming). e.g you can use friends, family, coworkers.
- of opportunity
can produce a biased sample as the researcher may choose people from their own social and cultural group to participate.
sample not representative of your target population as you friends may have different qualities to people in general.
volunteer
ppts volunteer when asked to or in response to an advert.
+ of volunteer
- quick + easy
- reaches wide variety of ppt
- of volunteer
type of participants who volunteer may not be representative of the target population for a number of reasons. those with strong views for the subject are more likely to participate.
random
a sample in which every member of the population has an equal chance of being chosen
+ of random
gives an unbiased representative sample of a target population, high gen
- of random
- time consuming and is often impossible to carry out when you have a large target population
stratified
classifying the population into categories and then choosing a sample which consists of participants from each category in the same proportions as they are in the population
+ of stratified
unbiased rep sample, high gen
- of stratified
- time consuming as the categories have to be identified and calculated
- if you do not have details of all the people in your target population you would struggle to conduct a stratified sample
