Types of Experiment

• Laboratory experiments are in a controlled environment where extraneous and confounding variables are controlled. The IV is then manipulated and the effect on the DV is recorded.

  
  

  +) Greater controls means less extraneous variables meaning that its more easily replicated meaning the findings can be confirmed.

  
  

  -) A controlled lab enviorment is artificial and participants are actively aware that they are being studied. Thus, behaviour may not be natural and cannot be generalised to everyday life. (i.e. low external validity).
• Field experiments are conducted in a natural setting

  
  

  +) A more natural environment means that participants are more comfortable and their behaviour is more authentic, results may generalise to everyday life.

  
  

  -) 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 researcher doesn't manipulate the IV. This is because something else causes the IV to vary. As a result, the DV may be naturally occurring.

  
  

  +) Better external validity because it involves real world issues, such as the effect of natural disaster on stress levels.

  
  

  -) The natural event may only occur rarely which means that this reduces the opportunity for research.
• Quasi-experiments are when the IV is a pre-existing difference between people and no one has manipulated this variable.

  
  

  +) This type of experiment is often carried out under controlled conditions and therefore shares the strengths of lab experiments.

  
  

  -) Participants are not randomly allocated because the experiment has no control over which participants are placed in which condition because the IV is pre-existing.