types of experiments

• laboratory experiments

  • conducted under controlled conditions that are artificial.
  • involves the researcher manipulating the IV whilst measuring the DV.
  • not necessarily carried out in a laboratory, it can be any experiment that the researcher can control.
  • there is both an experimental and control condition.
  • the researcher randomly allocates the ppts to either the experimental or control conditions.
• laboratory experiments - s/w


  • high level of control - we can therefore infer that the IV caused the DV.
  • easy to replicate, so reliability can be checked.
  • cannot be generalised to real life, so results have low ecological validity than other methods.
  • demand characteristics - if ppts are aware they are in a study they may act in a certain way and affect validity.
• field experiments 


  • an experiment conducted in a natural environment.
  • the IV is still being manipulated by the researcher, so causal relationships can be formed.
  • the DV is still measured.
  • ppts are unaware they are being researched.
• field experiments - s/w


  • higher ecological validity than lab experiments as they are conducted in a real situation without the control of an experimenter.
  • less demand characteristics, as ppts are usually unaware that they are taking part, so results are more valid.
  • unethical - since the ppts are unaware that they are taking part in the research, there is less chance that the researcher can reach out to debrief them.
  • more chance of extraneous variables affecting the results because there is less control than in a laboratory experiment.
• quasi and natural experiments 


  • a quasi experiment is not a "true" experiment because the researcher has not deliberately manipulated an IV, and ppts are not randomly allocated to an experimental or control condition.
  • methods within this category include natural experiments and difference studies.
  • a research method where the IV arises naturally, although the DV still can be measured in a laboratory or any other location of the researcher's choice.
• Quasi experiments allow research where the independent variable (IV) can't be manipulated for practical or ethical reasons, allowing a range of behaviours to be investigated.
• It is not ethically or practically possible to cause someone to develop a mental illness such as depression or schizophrenia.
• Quasi experiments allow researchers to investigate "real" problems, such as the effects of a disaster on health, which can help a greater amount of people in more situations.
• Quasi experiments cannot demonstrate causal relationships because the independent variable (IV) isn't manipulated directly, so we cannot be sure that the IV caused the dependent variable (DV).
• Quasi experiments face a threat to internal validity due to there being less control of extraneous variables that could be the reason for the dependent variable (DV) rather than the independent variable (IV).
• what is an experiment

  a research method where cause and effect is measured, through the control and manipulation of key variables, and where the participants are randomly allocated to experimental/control groups.
• participant observation


  • method where the researcher takes on the role of a participant whilst observing other participants behaviour around them.
  • the researcher becomes part of the group, and does not reveal who they are.
• participant observation - s/w

  • reduces demand characteristics, as participants are unaware that they are being observed by the researcher
  • can research people who would otherwise by very difficult to observe, so the researcher may end up finding out information they didn't know existed.
  • researcher may suffer from observer bias - the researcher's expectations affect their perception of events and they become subjective
  • unreliable findings because it is difficult to take notes during the observation, so data relies on memory.
• non-participant observation

  • method where the researcher watches and records participants' behaviour without interfering in any way.
  • the participants are unaware that they are being observed.
• non-participant observation - s/w

  • observer doesn't take part in the action, but instead watches from a distance, so less chance of observer bias
  • researchers can see how participants behave rather than relying on self reports, which may produce more valid and reliable findings.
  • observer bias
  • unethical, because participants do not always know they are being observed.