Sampling Flashcards
Target Population
The set of people researchers want to find out about.
Sample
A small set of people taken from the target population.
Sample Frame
The source material from which a sample is drawn.
Representative
How well a sample reflects the target population.
Opportunity Sample
Researcher uses people who are available at that time because it is easy and convenient.
Opportunity Sample (Advantages)
-Quick and cheap
-Good for characteristics that we can assume are the same for everyone
-Only sampling method for some research methods (covert field experiment).
Opportunity Sample (Disadvantages)
-Sample bias (probably similar culture, researcher might choose helpful looking people)
-Can decline to take part, so turns into volunteer sampling.
Self-Selected Sampling
Researcher uses people who take part in a study because they volunteer when asked or have responded to an advert.
Self-Selected Sampling (Advantages)
-Quick and Practical
-Can reach wider variety of participant.
-Ethical, participants consent to taking part.
Self-Selected Sampling (Disadvantages)
-Sample bias (biased towards the type of person who volunteers for research).
Random Sampling
Every member of the target population has to be available to the researcher.
Each person has an equal chance of being picked.
Random Sampling (Advantages)
-Provides unbiased sample, most likely to be most representative.
Random Sampling (Disadvantages)
-Time Consuming and often impossible
-If you have to ask permission it becomes volunteer research.
Systematic Sampling
A whole list of the target population is needed to select participants from.
Names are systematically taken from each register, e.g. every 10th name.
Systematic Sampling (Advantages)
-Provides unbiased sample, participants selected using an objective system.
Systematic Sampling (Disadvantages)
-Not truly random unless you select a number using a random method.
Stratified Sampling
Selecting participants in proportion to their frequency in the target population. Subgroups in the target population are identified and participants are selected at random for the sample in the same proportions.
Stratified Sampling (Advantages)
-Most representative of target population as all subgroups are represented so we can generalize the results.
-It produces more precise estimates for subgroups than simple random sampling.
Stratified Sampling (Disadvantages)
-It can be difficult to access a list of the entire population and classify every member into a sub group.
-Very time consuming to identify and allocate to subgroups to make sure that the sampling frame is truly representative to the target population.
Quota Sampling
The same process as stratified sampling (subgroups identified) BUT the researcher chooses (using opportunity sampling) who becomes part of the sample for each subgroup.
Quota Sampling (Advantages)
-Most representative of target population as all subgroups are represented so we can generalize the results.
Quota Sampling (Disadvantages)
-It may increase the risk of researcher bias, as the researcher might choose people who are easy to approach or co-operative.
-It does not allow random selection of participants, which may introduce bias or inaccuracy.
-Very time consuming to identify and allocate to subgroups to make sure that the sampling frame is truly representative to the target population.
What is the difference between Stratified and Quota Sampling?
Stratified- Once the characteristics of the target population are identified each participant is chosen RANDOMLY.
Quota- Once the characteristics of the target population are identified each participant is chosen via OPPORTUNITY SAMPLING- so participants don’t have equal chance of participating.
Snowball Sampling
Snowball sampling is a non-probability sampling method where new units are recruited by other units to form part of the sample. Snowball sampling can be a useful way to conduct research about people with specific traits who might otherwise be difficult to identify (e.g., people with a rare disease).
