Sampling, Ethical issues, Pilot studies & Peer review Flashcards
What is a pilot study?
A small-scale trial of the research design, prior to the full-scale study with the purpose to identify problems with the design, method or analysis so that they can be fixed before the full-scale study is carried out
Why might a pilot study be used?
- to check that instructions are standardised and the instructions given to the participant are clear to understand and that they have enough time to carry out tasks given
- participants can be asked about possible problems and suggest changes
- saves time and expense
What is the target population?
the group of people to whom the researchers wish to generalise their findings
What is the sample?
the group of people that take part in the study and a representative sample is a sample who are typical (representative) of the target population
What is the sampling frame?
the source material from which the sample is drawn, list of all those within population who can be sampled, may include individuals, households or institutions, must be representative of the population
What is sampling bias?
a systematic error due to a non-random sample of a population, causing some members to be less likely to be included than others, resulting in a biased sample
What is random sampling?
every member of the target population has an equal chance of being detected to be in the sample
What are the strengths of using random sampling?
- reduces the change of a biased sample (avoids bias) as every member of the target population has an equal change of being selected
- as sample is less likely to be biased, more likely to be representative of the target population and results can be generalised to that population
What are the disadvantages of random sampling?
- almost impossible to obtain a truly random sample as all names in target population may not be known - problem finding suitable sampling frame
- some selected may choose not to take part, then the kind who do take part are over-represented, causing the sample to be biased
- some methods, may not be possible
- of the populations is very heterogeneous, the results can vary considerably from one sample to another
What is systematic sampling?
a system to select who will be asked to participate, choosing every nth number from a list of the population (n is the sampling interval)
What are strengths of systematic sampling?
- reduces the chances of investigator bias in selection
- easier to carry out random sampling, with less chance of mistake - particularly useful with large populations
What are the limitations of systematic sampling?
- cannot guarantee everyone will want to take part
- if there’s a periodic pattern in the list, results may be biased
- may not be possible (field or natural)
What is stratified sampling?
when the population is divided into non-overlapping categories (strata), divide how to stratify the population, then ascertain what % of the entire population is in the strata - size of sample from each strata needs to be PROPORTIONAL to the number of people from the population in it
then obtain sample from within strata using random sampling
What are the strengths of stratified sampling?
- if population is heterogeneous, gives a more realistic picture than random sampling and ensures the representation on key strata
What are the limitations of stratified sampling?
- detailed information atout the population is required to define the strata, which may be very difficult to obtain
- crucial to use correct stratification according to factors that affect investigation - may not be known what these are in advance
What is opportunity sampling?
uses participants from the target population who are available at the time
What are the strengths of opportunity sampling?
- quick and easy to do (inexpensive)
- face-to-face ethical debriefings and debriefings can be undertaken
What are the disadvantages of opportunity sampling?
- samples potentially biased as participation depends on availability at the time of the research, location will also be a source of bias
- researcher may introduce bias by only approaching individuals they find appealing