Target Population / Population
an entire group with specified characteristics. The target group/population is the desired population subgroup to be studied, and therefore want research findings to generalise to
What are the 4 main sampling methods?
Opportunity
Volunteer
Random
Stratified
Random Sampling
Everyone in the entire target population has an equal chance of being selected.
Random samples are the best method of selecting your sample from the population of interest.
The advantages are that your sample should represent the target population and eliminate sampling bias, but the disadvantage is that it is very difficult to achieve (i.e. time, effort and money).
Stratified Sampling
The researcher identifies the different types of people that make up the target population and works out the proportions needed for the sample to be representative.
A list is made of each variable (e.g. IQ, sex etc.) which might have an effect on the research. For example, if we are interested in the money spent on books by undergraduates, then the main subject studied may be an important variable.
For example, students studying English Literature may spend more money on books than engineering students so if we use a very large percentage of English students or engineering students then our results will not be accurate.
We have to work out the relative percentage of each group at a university e.g. Engineering 10%, Social Sciences 15%, English 20%, Sciences 25%, Languages 10%, Law 5%, Medicine 15% The sample must then contain all these groups in the same proportion as in the target population (university students).
Gathering such a sample would be extremely time consuming and difficult to do (disadvantage). This method is rarely used in Psychology. However, the advantage is that the sample should be highly representative of the target population and therefore we can generalize from the results obtained.
Opportunity Sampling
Uses people from target population available at the time and willing to take part. It is based on convenience.
An opportunity sample is obtained by asking members of the population of interest if they would take part in your research. An example would be selecting a sample of students from those coming out of the library.
This is a quick way and easy of choosing participants (advantage), but may not provide a representative sample, and could be biased (disadvantage).
Volunteer Sampling
People come forward and volunteer themselves, but may not be representative of a target population
