experimental methods

• Experiment

  An investigation in which a hypothesis is scientifically tested. An independent variable (the cause) is manipulated, and the dependent variable (the effect) is measured; any extraneous variables are controlled.
• Advantages of experiments

  • They should be objective - the researcher's views and opinions should not affect a study's results, making the data more valid and less biased.
• Ecological validity


  The degree to which an investigation represents real-life experiences.
• Experimenter effects


  The ways that the experimenter can accidentally influence the participant through their appearance or behavior.
• Demand characteristics


  The clues in an experiment that lead the participants to think they know what the researcher is looking for (e.g., the experimenter's body language).
• Independent variable (IV)


  The variable the experimenter manipulates (i.e., changes) and is assumed to have a direct effect on the dependent variable.
• Dependent variable (DV)


  The variable the experimenter measures. This is the outcome (i.e., the result) of a study.
• Extraneous variables (EV)


  All variables which are not independent variables but could affect the results (DV) of the experiment. EVs should be controlled where possible.
• confounding variables

  Variables that have affected the results (DV), apart from the IV

  • could be an extraneous variable that has not been controlled.
• Random allocation


  Randomly allocating participants to independent variable conditions means that all participants should have an equal chance of participating in each condition.
• Order effects

  Changes in participants' performance due to their repeating the same or similar test more than once, such as practice effect and fatigue effect.
• Experimental method


  Manipulation of an independent variable (IV) to have an effect on the dependent variable (DV), which is measured and stated in results