Types of experiment

• Lab experiment


  • conducted in a lab/ controlled environment
  • isolation of IV by maintaining a strict control of extraneous variables
  • control group used
• Strengths - lab experiment

  • control of extraneous variables
  • high validity
  • most certainty of cause and effect
  • high reliability due to a high level of control
• Weaknesses - lab experiment

  • lack ecological validity- not in natural setting
  • lack mundane realism
  • greater chance of demand characteristics
• Field experiments


  • researcher still manipulates the IV and records effects on DV but tries to control it as much as possible
  • carried out in Ps natural environment
• Strengths - field


  • still try and control as much as possible - more reliable than natural but less than labs
  • higher ecological validity than lab
• Weaknesses - field


  • less certainty of cause and effect
  • ethical issues around consent to take part and ability to debrief
• Natural experiment


  • IV not manipulated by researcher and would happen even if researcher not there
  • records effect on DV before and after event
• Strengths - natural

  • provide chances to study things that wouldnt be able to be directly manipulated
  • high external validity
• Weaknesses- natural


  • not carried out often due to rarity of events
  • high ecological validity as it is a real event and mirrors real life situations
• Quasi experiments


  • not a true experiment
  • cannot randomly assign Ps to groups
  • IV based on existing diff between people
  • cannot randomly allocate so there may be confounding variables
• Strengths - quasi


  • high validity and reliablity if carried in a controlled environemnt
• Weaknesses - quasi


  • cannot randomly allocate- likely to be confounding variables
  • IV not deliberately changed by researcher and so researcher cannot claim the IV caused a change on the measured behvaiour
• True experiment


  one where Ps ca be randomly allocated

  e.g. lab and field