SAMPLING Flashcards
What is the population?
The population refers to the large group of individuals that a particular researcher may be interested in studying (e.g. students attending colleges in the North West). This is often called the target population because it is a subset of the general population.
Why is the ‘population’ sometimes referred to as the ‘target population’?
The population is sometimes called the target population because it is a subset of the general population.
From the target population, researchers select a smaller sample. What is a sample?
The sample is a group of people who take part in a research investigation. The sample is drawn from a target population and is presumed to be representative of that population.
Why does a sample have to be selected from the target population?
For practical and economic reasons, it is usually not possible to include all members of a target population in an investigation so a researcher selects a smaller group, known as the sample.
Why is it important for the sample to be representative of the target population?
It is important for the sample to be representative of the target population because this enables generalisation of findings to become possible. Generalisation refers to the extent to which findings and conclusions from a particular investigation can be broadly applied to the population.
Samples are often criticised for being bias. What does the ‘term’ bias refer to?
In the context of sampling, bias refers to when certain groups may be over or under-represented within the sample selected. For example, there may be too many younger people or too many people of one ethnic origin in a sample. This limits the extent to which generalisations can be made to the target populations.
How are samples selected by the researcher?
Sampling techniques are used by researchers to select their samples.
What are sampling techniques?
Sampling techniques refer to the methods used to select people from the population.
Within psychology there are five major sampling techniques. Name these five samples,
- Random sample
- Systematic sample
- Stratified sample
- Opportunity sample
- Volunteer sample
What is a random sample?
A random sample is a sophisticated form of sampling in which all members of the target population have an equal chance of being selected.
How are random samples conducted by the researcher?
Firstly, a complete list of all members of the target population is obtained.
Secondly, all of the names on the list are assigned a number.
Thirdly, the sample is generated through the use of a computer-based randomiser or by picking numbers from a hat.
What are the strengths associated with random samples?
A random sample is free from researcher bias. The researcher has no influence over who is selected and this prevents them from choosing people who they think may support their hypothesis.
What are the weaknesses associated with random samples?
Random sampling is difficult and time-consuming to conduct. A complete list of the target population may be extremely difficult to obtain.
A researcher may end up with an unrepresentative sample. The laws of probability suggest that random sampling is likely to produce a representative sample, however, it is still possible that the random method may select all females or all males.
Selected participants may refuse to take part.
What is a systematic sample?
A systematic sample is when every nth member of the target population is selected (e.g. every 5th pupil on a school register).
How is a systematic sample conducted by a researcher?
A sampling frame is produced, which is a list of people in the target population organised into, for instance, alphabetical order. A sampling system is nominated or this interval may be determined randomly to reduce bias. The researcher then works through the sampling frame until the sample is complete.
