Research issues

• The independent variable (IV) should be the only factor that affects the dependent variable (DV). Anything else that could affect the dependent variable (DV) should be taken out or controlled
• Extraneous variables: These are any variables other than the IV that could or may affect the DV if it is not controlled. They are essentially 'nuisance' variables that psychologists want to minimise and, therefore, control. Does not vary systematically with the IV & can often be controlled before the experiment begins
• Confounding variables: any variable that affects the DV. They do change and vary systematically with IV so we cannot be sure what caused the change in the DV. We cannot tell if any change in the DV is due to the IV or the confounding variable
• Extraneous variables can be subdivided into participant variables and situational variables
• Participant variables are any individual differences between participants that may affect the DV
• Situational variables are any features of the experimental situation that may affect the DV
• Demand characteristics: any cue from the researcher or research situation, which may mean the participants 'workout' what the purpose of the investigation is which results in participant reactivity and means they change their behaviour
• Single blind: this is when the participants are not told the true aim of the research. This is an attempt to control for the confounding variable of demand characteristics
• Investigator effects: any effect on the investigator's behaviour/appearance (conscious or unconscious) on the DV
• Double blind: this is when the participants are not told the true aim of the research and the researcher does not know them either. in this case, a third-party researcher will conduct the experiment. this also helps to reduce demand characteristics and investigator effects
• Randomisation: a way of trying to control any bias in the groups or conditions of an experiment
• Carrying out randomisation:

  • materials used
  • assigning participants to groups
  • order of the condition
• Standardisation: using the same format/procedures/instructions for all participants in the study