types of experiments

• laboratory experiments are controlled environments where extraneous and confounding variables can be regulated. The independent variable is manipulated and the effect on the dependent variable is recorded
• strengths of laboratory experiments are:

  • extraneous and confounding variables can be controlled- this means that the effect of extraneous and confounding variables on the dependent variable can be minimised. Cause and effect between the independent and dependent variable can be demonstrated (high internal validity)
  • can be more easily replicated- greater control means less chance that new extraneous variables introduced. This means that findings can be confirmed, supporting their vadility
• Limitations of laboratory experiments are:

  • may lack generalisability- the controlled lab environment may be rather artificial and participants are aware they are being studied. Thus behaviour may not be natural and can't be generalised to everyday life (low external validity)
  • demand characteristics may be a problem- these are cues in the experimental situation that invite a particular response from participants. The findings may be explained by these cues rather than the effect of the independent variable (low internal validity)
• field experiments occur in a natural setting where the independent variable is manipulated.
• strengths of field experiments:

  • more natural environment- participants are more comfortable and behaviour is more authentic. Results may be more generalisable to every day life
  • participants are unaware of being studied: participants are more likely to behave as they normally do so the findings can be generalised. The study has great external validity
• limitations of field experiments:

  • more difficult to control extraneous and confounding variables- observes changes in the dependent variable may not be due to the independent variable, but to extraneous and confounding variables instead. It is more difficult to establish cause and effect than in the lab
  • there are ethical issues- participants in a field experiment may not have given informed consent. This is an invasion of participants privacy which raises ethical issues
• natural experiments are when the experimenter doesn't manipulated independent variable. It does change, but the change is not made by the experimenter, someone or something else cause is the independent variable to vary. The dependent variable maybe naturally occurring or maybe devised by the experimenter and measured in the field or lab
• Strengths of natural experiments:

  • may be the only practical/ethical option- it may be unethical to manipulate the independent variable like studying the effects of institutionalisation on children. And natural experiment may be the only way casual research can be done for such topics
  • greater external validity- natural experiments involve real world issues, such as the effect of a natural disaster on stressful events. This means the findings are more relevant to real experiences
• Limitations of natural experiments:

  • the natural event may only occur rarely- many natural events are one-offs and this reduces the opportunity for research. This may limit the scope for generalising findings to other similar situations
  • participants are not randomly allocated- the experiment has no control over which participants are placed in which condition as it independent variable is pre-existing. This may result in confounding variables that aren't controlled
• Quasi experiments is when the independent variable is based on a pre-existing difference between people like age or gender. The dependent variable maybe naturally occurring or maybe devised by the experimenter and measured in a field or lab
• strengths of quasi experiments:

  • there is often high control- often carried out under controlled conditions and therefore shares some of the strengths of lab experiments. This means replications possible
  • comparisons can be made between people- in a quasi experiment the independent variable is a difference between people like people with and without autism. This means that comparisons between different types of people can be made
• limitations of quasi experiments:

  • Participants are not randomly allocated– the experiment has no control over which participants are placed in which condition as the independent variable is pre-existing. Participant variables may have caused the change in the dependent variable acting as a confounding variable
  • casual relationships not demonstrated- as with a natural experiment, the researcher doesn't manipulate or control the independent variable. We cannot stay for certain any change in the dependent variable was due to the independent variable