validity

• internal validity

  the study measures what it intends to measure, the effects on the DV are caused by the IV, meaning the findings are accurate.
• external validity 


  whether the study paints a true picture of real-life behaviours (mundane realism,) and would apply to different places, times or people (population validity.)
• researcher bias 


  double-blind procedure will prevent researcher bias as the researcher does not know the aim and therefore cannot give hints or tips to ppts.

  • also reduces demand characteristics, as the ppts won't change their behaviour accordingly.
• social desirability + demand characteristics

  1. single-blind procedure, where the ppts are unaware of the true hypothesis until after their role in the research is complete.
  2. where the purpose of the research is obvious, psychologists should explain the importance of ppts providing accurate and honest responses, by giving ppts anonymity and privacy when they give their answers.
  3. the use of independent groups would also reduce these validity issues.
• changes to the location of the research and nature of the task can improve validity - ensuring that research is conducted in the field rather than the lab.
• changes to the sampling technique and target population can also improve external validity.