Reliability and Validity

• what's internal reliability?


  measure of the extent to which something is consistent within itself- refers to whats going on inside the study
• how can internal reliability be assessed?


  split- half method

  • to compare a person's performance on 2 halves of a questionnaire/ test. If the test is assessing the same thing in all questions there should be a close correlation in the scores derived from both halves of the test.
• How to improve reliability?


  Lab experiment: standardised instructions, variables operationalised, can be replicated easily

  Interview/questionnaire: pilot study, researchers trained

  Observation: filming behaviour, inter observer reliability
• What's internal Validity?


  Whether the researcher tested what they intended to test. Concerns what goes on inside a study
• How to assess internal validity?


  Face Validity- refers to whether at face value the study appears to measure what it's set out to do. More worthwhile if opinion is taken from an expert .

  Concurrent validity- compares a new test to other tests to see if they produce similar results. If tests agree they have concurrent validity.
• What is external validity?


  External validity refers to the extent to which the findings of a study can be generalized to other populations, settings, or conditions.
• How to assess external validity?


  Population Validity- extent to which results from research can be generalised to other groups of people.

  Ecological validity- extent to which results from research can be generalised to situations outside the research settings

  Temporal validity- measures whether findings from a particular study or concepts from theories are true over time
• improving internal validity 


  • lab experiments- extraneous variables need to be tightly controlled
  • field- extraneous variables need to be controlled
  • observations- more than 1 observer should be used, well trained
• improving external validity 


  • lab- sampling technique needs changing, replicating study to improve population validity, increasing sample size
  • field- sampling technique, replicating, increasing sample size, ensure pp don't know they're taking part
  • observation- observe as many pp as poss, use covert observations