participant sampling techniques

• random: where participants all have an equal chance of being selected

  • fair method as everyone has an equal chance of being selected.
  • may end up with a biased sample - since the selection is due to chance, there may be certain subgroups of the target population that are over or underrepresented in the sample.
• Opportunity sampling is a type of sampling where participants are selected at the researcher's convenience, such as picking people who were there at the time in a specific location.
• Opportunity sampling is much easier for the researcher to use in comparison to other sampling techniques, which may be more costly in time and resources.
• Opportunity sampling may end up with a biased sample, as the selection was whomever was easier to access at the time and people tend to live in cliques or groups of people with whom they share many attributes with.
• Opportunity sampling may be unethical to ask a potential group of participants to be in your research, for example, some students may feel obliged to take part in the research projects of their university professor, meaning they aren't really giving valid consent.
• systematic sampling: where every nth person on a list is selected by the researcher.


  • as long as the first ppt is selected randomly, then the researcher cannot be accused of being biased in their selection of ppts.
  • may still end up with a biased sample since the selection is still due to chance, there may be certain subgroups of the target population that are over or underrepresented in the sample.
• stratified sampling: where the target population is divided into subgroups, then the ppts are selected randomly from each subgroup.


  • we can guarantee that all subgroups in the target population will be represented in the sample.
  • more difficult for the researcher to administer in comparison to other sampling techniques, which may be less costly in time and resources.
  • the ppts randomly selected from each subgroup may not be representative of that subgroup.
• quota sampling: target population is divided into subgroups, and the participants are chosen from each subgroup at the convenience of the researcher.


  • We can guarantee that all subgroups in the target population will be represented in a sample.
  • More difficult for the researcher to administer in comparison to other sampling techniques.
  • Participants opportunistically selected from each subgroup may not be representative of that subgroup.
• Self selected sampling: where participants volunteer for research. 


  • Unlike all other sampling techniques, we know that participants are interested in taking part.
  • People who volunteer may not be from appropriate subgroups within the target population.
  • Research may not have sufficient participants who are willing to take part.
• Snowball sampling: where participants are initially recruited by the psychologist and then those participants recruit further participants from people they know.
• Snowball sampling is a helpful sampling technique when trying to investigate a rare characteristic or behaviour.
• Snowball sampling is more time consuming than other sampling techniques as the researcher is having to wait and rely on their initial participants being able to contact other people who share their rare characteristic.
• The initial participants the researcher identifies may not know enough participants who share their rare characteristic.
• Event sampling: where participants are observed by a psychologist who records a specific behaviour (event) each time it occurs to create a total score.
• Event sampling records all the events during an observation, unlike time sampling.
• Event sampling is more straightforward as it only requires identifying a start and finish time, rather than recording each event in the correct interval.
• Event sampling is limited as it lumps all of the events together, making it difficult to determine if a behaviour is more common at the start, middle or end of the observation.
• Event sampling can also be overwhelming for the researcher, as they are trying to record all events all the time.
• Time sampling: where a psychologist observes and records behaviour at specific time intervals, and then creates an average score for each participant being observed.
• Time-point sampling: a research method where researchers do not get overwhelmed with data throughout the observation, which can happen with event sampling.
• Limited because it may only record events or behaviours that occur at a specific point in time; if that behaviour isn't occurring at a specific point in time that the researcher records the behaviour, then the behaviour goes unrecorded, unlike in event sampling.
• More complex to organise than event sampling as the researcher needs to keep track of the different time intervals when they were recording events, which can be quite difficult if they're observing multiple behaviours or participants.