Research Methods - sampling methods Flashcards
What is a target population?
Group of people you intend to generalise your findings to
What is a sampling frame?
List of all names/members in a target population
What is a sample?
Small group of people that represent the target population (needs to be representative so the results can be generalisable)
What is random sampling?
Every member of the target population has an equal chance of being selected
How do researchers carry our random sampling?
1) Get a sampling frame
2) Put all names in container (or assign them a number)
£) Select X names out the container (or use random number generator) to go into condition 1, then repeat for condition 2
What are the strengths of random sampling?
No researcher bias so is more likely to be representative of the target population
What are disadvantages of random sampling?
- Hard to get a sampling frame (more time and effort)
- Not completely representative so could reduce generalisability of results
What is opportunity sampling?
Recruiting anyone who happens to be available at the time of the study
How do researchers carry out opportunity sampling?
Researcher will go somewhere that they are likely to find that specific target population
What are strengths of opportunity sampling?
- Simple, quick and easy
- People with certain characteristics can be found
What are weaknesses of opportunity sampling?
Unrepresentative so can’t confidently generalise results
What is volunteer sampling?
People actively volunteer by responding to a request (advertised)
How do researchers carry out volunteer sampling?
Ppts. self-select by responding to an advert and then research selects only those that are suitable for the study
What are strengths of volunteer sampling?
- Most convenient and economical method
- Can reach a wide audience (digital adverts)
- Gets a motivated sample with lower attrition rates
What are the weaknesses of volunteer sampling?
Sampling bias as particular people (altruistic) or interested in the topic could lead to similar characteristics affecting the results
What is systematic sampling?
Selecting names from a sampling frame at regular intervals
How do researchers carry out systematic sampling?
1) Produce a sampling frame (typically in alphabetical order)
2) Sampling system nominated (every nth person) - dividing sample size by how many ppts. needed to find n
3) Researcher works through sampling frame until sample is selected
What are strengths of systematic sampling?
Population is evenly sampled using an objective system (reducing researcher bias) and increasing chances of a representative sample
What are weaknesses of systematic sampling?
Not truly unbiased/random as not all people have an equal chance of being selected so representation isn’t guaranteed
What is stratified sampling?
Dividing population into strata (sub-groups) based on certain characteristics and then selecting samples randomly from each stratum, keeping them proportionate
How do researchers carry out stratified sampling?
1) Identify how many ppts. in each strata
2) Work out % of each strata that makes up the target population
3) Use random sampling to select a sample by picking specific number of ppts. from each sample (randomly)
What are strengths of stratified sampling?
Most representative method as there’s an equal representation of each sub-group (generalisability is high)
What are weaknesses of stratified sampling?
- Knowledge of population characteristics required which may not be available
- Time consuming to divide population into stratums and then randomly selecting from each can take time
