Research issues:

• What is an extraneous variable?

  Any variable, other than the independent variable (IV), that may affect the dependent variable (DV) if it is not controlled. EV's are essentially nuisance variables that do not vary systematically with the IV.
• What are the different types of extraneous variable?

  1. participant variables
  2. situational variables
  3. Order effects
• What needs to happen to extraneous variables?

  They should be identified and controlled to prevent them from becoming confounding variables
• What are participant variables?

  Characteristics of the participants
• When do participant variables act as extraneous variables?

  When an independent groups experimental design is used
• What happens in an independent groups experimental design?

  A group of participants is tested in each condition
• Why might participants in one condition perform better than others?

  Due to shared characteristics rather than the IV
• When do participant variables become extraneous variables?

  If they are relevant to the dependent variable
• How do participant variables affect the validity of an experiment?

  They can introduce bias if not controlled
• Control of participant variables:

  • Random allocation can be used to control ppt variables
  • This is when ppts are randomly allocated to different conditions of the IV
  • Random allocation can be achieved using either the lottery method (where each ppt is given a number and numbers are drawn out of a hat) or a random number generator (where each ppt is given a number and a random number generator is used to select numbers)
• Situational variables:

  • Situational variables are features of the environment that can affect the results of the experiment
  • For example, temperature, time of day and noise level are all situational variables that can act as extraneous variables
  • However, these situational variables will only act as extraneous variables if they are relevant to the DV
• Control of situational variables:

  • Standardisation can be used to control situational variables
  • This is when procedures and instructions are standardised (kept the same)
  • This means all ppts should be subject to the same environmental conditions
• Order effects:

  • Order effects only act as an extraneous variable when a repeated measures experimental design is used
  • This is when the same group of ppts are tested in all conditions of the IV
  • Ppts may underperform in the second condition due to tiredness/boredom or over perform in the second condition due to practice
• Control of order effects:

  • Counterbalancing can be used to control order effects
  • This is when half of the participants experience condition A followed by condition B and the other half of the ppts experience condition B followed by condition A
  • Any order effects in each group will cancel each other out
• What leads to demand characteristics and investigator effects?

  • ppts are not passive within experiments and are likely to be spending much of their time trying to make sense of the new situation they find themselves in
  • This leads to demand characteristics and investigator effects, both of which also act as extraneous variables
• What are demand characteristics?

  Cues that help participants guess the experiment's aim
• How do demand characteristics affect participant behavior?

  They cause participants to act unnaturally
• Why might participants change their behavior in an experiment?

  To please the researcher based on expectations
• What might participants do to sabotage an experiment due to demand characteristics?

  Act in a way they think is unexpected
• When are demand characteristics more likely to be a problem?

  When a repeated measures design is used
• What is a repeated measures design?

  Same group of participants tested in all conditions
• Why are participants more likely to guess the aim of the experiment in a repeated measures design?

  They experience all conditions of the independent variable
• Control of demand characteristics:

  • Demand characteristics are very difficult to control
  • The best way to avoid them is to use an independent groups design
  • This is when a different group of ppts are tested in each condition of the IV
  • In some cases, a single-blind can also be used to reduce the risk of demand characteristics
  • This is when the ppt is unaware of the research aims and which condition of the IV they are experiencing
  • For example, in a drug trial, the ppt would not know whether they were taking the real drug or the placebo drug
• What are investigator effects?

  Effects of the researcher's behavior on outcomes
• How can a researcher's characteristics influence research outcomes?

  They may affect participant responses and behavior
• How might a female participant respond differently to a male researcher?

  She may be less willing to share sensitive information
• What role does a researcher's communication style play in research outcomes?

  It may influence participant responses and engagement
• How can a researcher unconsciously encourage a particular group of participants?

  Through their tone of voice and facial expressions
• In what way can a researcher's selection of participants influence outcomes?

  It may bias the results based on participant characteristics
• How might a researcher manipulate a memory study to influence results?

  By placing easier words at the beginning and end
• What is a potential consequence of a researcher consciously selecting easier words in a memory study?

  It may increase the chances of participants remembering
• What design can reduce the risk of investigator effects?

  Double-blind design
• What is a double-blind design?

  Both participant and researcher are unaware
• In a drug trial, who is unaware of the treatment condition in a double-blind design?

  Both participant and researcher
• What is the purpose of using a double-blind design?

  To reduce the risk of investigator effects
• In a drug trial, what might participants not know?

  Whether they are taking the real drug
• What does randomisation refer to in research design?

  Use of chance to reduce researcher influence
• How can randomisation be applied in a memory study?

  By determining word order by chance
• How does randomisation help in reducing investigator effects?

  It minimizes the researcher's influence on design
• What are the key features of a double-blind design?

  • Both participant and researcher are unaware
  • Reduces risk of investigator effects
  • Commonly used in drug trials