RESEARCH METHODS: sampling Flashcards
what is a population?
A group of people who are the focus of the researcher’s interest, from which a smaller sample is drawn.
What is a sample?
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.
what is random sampling and how is it conducted?
All members of the target population has an equal chance of being selected.
1. Obtain a complete list of all members of the target population.
2. Assign a number for all the names.
3. Use a lottery method or a randomiser to select sample.
What is systematic sample and how is it conducted?
A systematic sample is when every nth member of target population is selected. For example every third house on a street.
1. A sampling frame is produced, which is a list of people in the target population organised. eg in alphabetical order
2. A sampling system is nominated. eg every 3rd person
3. The researcher then works through the sampling frame until the sample is complete.
What is a stratified sample and how is it conducted?
A stratified sample is a sophisticated form of sampling in which the composition of the sample reflects the proportions of people in certain subgroups (strata) within the target population or the wider population.
- The researcher first identified each strata that makes up the population
- The proportion needed for the sample to be represented are worked out. eg one person from each strata ( subgroup)
What is a opportunity sample and how is it conducted?
Many researchers simply decide to select anyone who happens to be willing and available. The research is simply takes the chance to ask whoever is around at the time of the study.
What is a volunteer sampling how is it conducted?
A volunteer sample involves the participant selecting themselves to be part of the sample. The researcher may place an advert in a newspaper or on a common room noticeboard. Willing participants may simply raise their hand when the researcher asks.
Evaluate random sampling.
+ potentially unbiased. Confounding or extraneous variables should be equally divided between the different groups, enhancing internal validity.
- difficult and time-consuming to conduct. Complete list of target population may be extremely difficult to obtain.
-you may end up with a sample that is still unrepresentative
-selected participants may refuse to take part.
Evaluate systematic sampling.
+ this sampling method is objective. The researcher has no influence over who is chosen once the system for selection has been established.
-this method is time-consuming and participants may refuse to take part which result in a volunteer sample.
Evaluate stratified sampling.
+ produces a representative sample because it is designed to accurately reflect the composition of the population. This means that generalisation of findings becomes possible.
-stratification is not perfect, identified strata cannot reflect all the ways that people are different ,therefore complete representation of target population is not possible.
Evaluate opportunity sampling.
+ less costly in terms of time and money, list of members of the target population is not required, no need to divide the population into different strata as there is in stratified sampling.
-opportunity sample suffer from two forms of bias: sample is not a representative of target population as it is drawn from a very specific area so findings cannot be generalised to the target population. Researcher has complete control over the selection of participants, they may avoid people they do not like the look of.
Evaluate volunteer sampling.
+ requires minimal input from the researcher, so is less time consuming than other forms of sampling.
+ research it ends up with participants who are more engaged.
-volunteer bias is a problem. Asking for volunteers may attract a certain profile of a person who is curious are more likely to please the researcher, this may affect how far findings can be generalised.
