Reliability

• Internal reliability


  The extent to which a test or measure is consistent within itself e.g. the use of standardised instructions and procedures for all participants
• External reliability


  The extent to which a test produces consistent results over several occasions
• Reliability issues

  • Lack of operationalisation of the variables
  • Order effects in repeated measures design
  • Lack of standardised procedures
  • Inconsistency of measuring tools
  • Uncontrolled environment
• Dealing with reliability issues

  1. Increasing levels of control in a study

  2. Using standardised procedure, instructions and scientific measuring equipment

  3. Conducting research in a laboratory environment
• Combatting order effects


  Counterbalancing - splitting population/sample into two halves, one completing condition 1 then 2, other completing condition 2 then 1
• Assessing reliability


  Measures used to check the consistency of a set of results/findings
• Split-half reliability/testing


  Splitting a participant's test answers in half and seeing whether they got the same or similar scores on the two halves
• Test-retest reliability


  Testing and retesting the same participants over time, with the same test, and comparing their scores
• Inter-rater reliability


  Two or more psychologists producing consistent results by using a standardised procedure, agreed coding system, or correlation of their data