How to improve validity

• Have clear controls

  • IV and DV
  • have controlled variables such as manipulating the IV to affect the DV
• Operationalising variables


  • Stated in a measurable form of the behaviour being measured/observed
  • How variables are measured
• Extraneous variables

  • Variables not being measured but could still effect the DV
  • Affects all participants
• Confounding variables

  • Variables not being measured but affect DV
  • Only affect some participants
• Partcipant effects

  • Demand characteristics: act unnaturally to prove or disprove hypothesis
  • (Social desirability bias or screw you effect)

  How to fix:

  • Single blind design
  • Independent groups
  • Realism
• Researcher bias

  • Experimenter influence behaviour consciously or unconsciously

  How to avoid:

  Standardisation

  Double blind design
• Whats a pilot study 


  • Initial run through of procedures of study to ensure no design flaws
• Confederate

  • A person playing a role in the study