variables & control of variables

• independent variable

  This is manipulated.
• dependent variable

  This is measured.
• extraneous variables

  Anything other than the IV that could change the DV. These can be controlled.
• confounding variables

  These are a type of extraneous variable that systematically change with the IV so it is hard to tell the cause and effect relationship between the IV and DV.
• demand characteristics

  Participants might not know how to act in experiments. Participants could guess what the researcher is investigating and change their behaviour to either help the results of hinder the results.

  Please-u effect = when the participants act how they think the researcher wants them to.

  Screw-u effect = when the participants act how they think the researcher does not want them to.

  
  

  Demand characteristics can be reduced if independent groups are used.
• investigator variables/ effects

  Anything about the investigator that could affect the results of research. The investigator could unknowingly encourage certain behaviours.
• participant variables

  Anything about the participant that could affect the results of research.
• situational variables

  Features of the research situation that could influence the participants behaviour.
• randomisation

  investigator + situational effects could be reduced through randomisation. A random generator could be used to decide different things like which participants take part in which conditions.
• standardisation

  Making sure that all participants have the same experiences.
• counterbalancing

  Can be used to reduce order effects - participants doing the same tasks but in different orders (ABBA).
• order effects

  If all participants do all of the tasks in the same order these could become a problem. People could get better at tasks etc - reduce this with counterbalancing.
• single-blind research

  The aims of the research are hidden from participants.
• double-blind research

  The aims of the research are hidden from the participants and researchers.