sampling methods Flashcards
What is sampling?
Choosing a smaller group of people from a larger group of people
What is a target population?
The group of people which any results would apply to e.g., teenagers
What are the different types of sampling method?
random, opportunity, self-selected (volunteer), snowball and stratified
What is random sampling?
When every member of the target population has an equal chance of being selected
How is a random sample conducted?
names out of a hat
What are strengths of a random sample?
- most unbiased and representative
- no influence of researcher bias
- results can be generalised
- has population validity
What are weaknesses of a random sample?
- difficult to access all the names of the whole target population
- sometimes not possible to achieve a random sample
- time-consuming
What is an opportunity sample?
A group of people who are available at the time of the study
What are strengths of an opportunity sample?
- quick and convenient
- less effort for the researcher
What are weaknesses of an opportunity sample?
- sample is likely to biased in terms of ethnicity and culture therefore be unrepresentative
- likely to lack population validity
What is a self-selected sample?
When a researcher places a advertisement about their study (poster) and participants respond and volunteer to take part
What do you put on a poster to gain a self-selected sample?
- target population
- details of the study
- contact information
What are strengths of a self-selected sample?
- informed consent
- less likely to drop out
- quick and convenient
What are weaknesses of a self-selected sample?
- low response rate
- small sample (not representative)
- results cannot be generalised as only a certain type of person would want to be a volunteer
What is a snowball sample?
A researcher recruits a participant that fits the target population then that person recruits their friends and so on
When is the snowball sample most commonly used?
When the target population does not have a list of names such as: drug dealers, criminals etc.
What are strengths of a snowball sample?
It makes it possible to include members of groups which are not easily accessible
What are weaknesses of a snowball strength?
- likely to be biased
- researcher may struggle to find the one participant to start the ripple effect
- results cannot be generalised
What is a stratified sample?
Made up of different layers of the population
What is the stratified sample equation?
sample size for each layer
size of whole sample
/
size of population
x
size of layer
