Sampling techniques and pilot studies Flashcards
what is a sample?
name given to the group of participants used in research
what is the target population?
everybody your research is meant to represent
what is a sampling frame?
a list of all the people forming a population from which a sample is taken
what is sample called if it is not representative?
biased
what are the 5 methods of choosing a sample?
-random sampling
-opportunity sampling
-stratified sampling
-self-selected or volunteer sampling
-systematic sampling
what is random sampling?
when every member of the target population has equal chance of being selected
explain briefly how random sampling works?
allocate each person of the target population a number and ask a random number generator to choose 100 numbers- the names against these numbers are the sample
what are strengths of random sampling?
-everybody has equal chance of being drawn
-avoids researcher bias
what are limitations of random sampling?
-requires access to all members of the target population (sampling frame)
-participants selected may not be willing to take part
-may produce sample which is unrepresentative of the target population
what is stratified sampling?
when the sample is manipulated to represent the target population. Important characteristics of the target population are listed and the sample is chosen that will represent each of these characteristics
what is the method for stratified sampling?
- divide target population into sub categories
- work out the proportion of each category needed in the sample
- select the number from each group using a random number generator (random sampling)
what are the strengths of of stratified sampling?
-representative of the target population
-avoids researcher bias
what are the limitations of stratified sampling?
-time consuming and costly
-requires access to all members of the target population (sampling frame)
-participants selected may not be willing to take part
what is an opportunity sample?
involves using participants who are easily available to the researcher
what are the strengths of opportunity sampling?
-easy to do and not time consuming
what are limitations of opportunity sampling?
-likely to produce a biased sample with similar characteristics
-participants selected may not be willing to take part
-sample may be unrepresentative of the target pop
-researcher bias
what is volunteer or self selected sampling?
participants put themselves forward to take part, usually in response to an advertisement
what are strengths of volunteer sampling?
-participants keen to take part
what are limitations of volunteer sampling?
-likely to produce a biased sample with similar characteristics
-volunteer bias
-may produce a sample which is unrepresentative of target population
-researcher bias
what is systematic sampling?
when every nth member of the target population is used
how is systematic sampling carried out?
a sampling frame is needed and the ‘system’ is used to choose the sample (e.g. every 3rd person)
what are strengths of systematic sampling?
-avoids researcher bias
what are limitations of systematic sampling?
-requires access to members of the target population
-participants selected may not be willing to take part
-may produce a sample which is unrepresentative of the target population
what is generalisation?
the extent to which findings from a particular study can be broadly applied to the pop.
what is bias?
when certain groups may be over or under-represented in the sample selected- which will affect how far results can be generalised
what is volunteer bias?
asking for volunteers may attract a certain type of person- which will affect how far results can be generalised
what is a pilot study?
a small scale run of the actual investigation to check that the process runs smoothly and see if any changes need to be made -it usually involves fewer participants than the main study
what sort of things are checked in a pilot study?
- have the participants fully understood the task (are the instructions clear?)
-have they been given enough time for the task?
-are materials used clear and appropriate? e.g. in a memory study this may be a word list
-in an observation are the behavioural categories clear?
-in an interview or questionnaire, are the questions clear? are there too many/ few? do changes need to be made?
