Validity

• Validity refers to accuracy
• What is internal validity

  • questions the cause and effect relationship between the manipulated independent variable and the dependant variable
  • if the change in the dependent variable was influenced by another factor the results lack internal validity
• What is external validity?

  • questions if the findings of the study can be generalised
  • if the sample can be used for the whole target population
  • if the findings can relate to real world settings and activities
• How may experiments lack internal validity?

  • social desirability bias
  • demand characteristics
  • investigator effects
  • extraneous variables - not using standardised procedures or not controlling participant variables through random allocation
• What are investigator effects?

  • the researchers behaviour influences the participants behaviour
  • researcher bias - they either consciously or unconsciously influence the results e.g. by positive body language or tone of voice when participants behave as expected
  • researcher could be biased on how they interpret participants behaviours and responses
• What is social desirability bias?

  • participants hide their genuine behaviours or opinions in order to respond in a more socially acceptable way - in order to " look good "
• What are demand characteristics?

  • participants discover the aim of the study and act in a way they believe will produce results supporting the researcher's theory
• Hoe can findings lack external validity?

  • they lack ecological validity
  • mundane realism
  • population validity
  • temporal validity
• What is ecological validity?

  • the extent to which the findings can be generalised to alternative environments
• What is mundane realism?

  • the extent to which the task is similar to stimuli in the real world
• What is population validity?

  • the extent to which the sample is representative of the target population
• What is temporal validity?

  • the extent to which the findings can be generalised to other time periods such as modern society
• How can we assess validity?

  • face validity
  • concurrent validity
  • predicative validity
• What is face validity?

  If a test appears to measure what it claims to be measuring
• What is concurrent validity?

  • the extent to which data from a newly created test is similar to an established test of the same variable conducted at the same time
  • a test of correlation is used to test this
• What is predicative validity?

  • the extent to which performance on a test can predict future outcomes or behaviours
• How can internal validity be improved?

  • random allocation - controls participant variables
  • standardised procedures - controls extraneous variables
  • counterbalancing - controls order effects
  • single and double blind trials - controls researcher bias and demand characteristics
  • peer review - controls researcher bias
• How can external validity be improved?

  • replicating findings in multiple settings (ecological validity)
  • replicating findings with diverse samples
  • replicating historical studies
  • replicating findings using realistic tasks