Types of Experiments

• What is an experiment?

  An experiment is where there is an independent variable (IV) that is changed so that an effect on the dependent variable (DV) can be observed.

  They aim to establish a cause and effect relationship – where the IV causes the DV results.

  To establish a cause and effect relationship it would have to be ensured that nothing other than the IV has an impact on the DV.
• Laboratory experiment

  Lab experiments are conducted in a deliberately constructed and controlled environment.

  The IV is set up and changed by the experimenter & DV measured by them – people are randomly allocated to a condition.

  Participants will know they are in a study.
• Laboratory experiment

  a researcher conducts a study examining whether people remember more words when learning them in silence or with noise playing in the background.
• Field experiment

  An experiment conducted in the “field” – so a real life setting for the behaviour of study.

  The IV is still manipulated by the experimenter and DV measured

  Participants are often unaware they are in the research
• Field experiment

  E.g. researchers were interested in whether members of the public would be more likely to help someone who has slipped and fallen if they are dressed as a business man or as a homeless man.
• Quasi experiment

  In a lab or in a real life setting BUT the key feature is it is not possible to randomly allocate participants to a condition. So participants are automatically assigned to a particular condition due to a characteristic of them - like Gender.

  That characteristic of them doesn’t change – i.e. their sex is set so they can only take part in one condition.
• Quasi experiment

  In a lab or in a real life setting BUT the key feature is it is not possible to randomly allocate participants to a condition.

  So participants are automatically assigned to a particular condition due to a characteristic of them - like Gender.

  That characteristic of them doesn’t change – i.e. their sex is set so they can only take part in one condition.
• Quasi experiment

  A study compares people with depression to those without depression.
• Natural experiment

  The IV is a naturally occurring event which by chance has more than one condition and would occur even if the experimenter didn’t study it.

  DV is measured by researchers but IV is not set up by them.

  Participants often unaware they are taking part.
• Natural experiment

  researchers investigated whether children on a remote island would be more aggressive after they have TV installed into their homes for the first time.