Reliability

• Reliability is when results are consistent when the study is replicated.
• Measurements to collect data:

  • Questionnaires and interviews - Using closed and open questions to measure opinions, personality traits and recalled past behaviours.
  • Experimental designs - Including biological devices (eg EEG), cognitive tests (Stroop test) or physical environment.
  • Observations - Clearly operationalised categories to classify observed beahviours.
• External reliability is the extent to which a measure is consistent when repeated (eg results are consistent with an exact replication at a different time and/or with different participants).
• Internal reliability is the extent to which different parts of a measure are consistent with itself (eg 100 question IQ test is divided into two 50 question tests, and the results for each would be similar).
• Assessing internal reliability - Split half method:

  1. Split participants in half.
  2. Participants complete both parts.
  3. Test the strength of correlation between the two parts.
  4. A strong correlation indicated internal reliability.
• Assessing external reliability - Inter-rater reliability:

  • Two or more observers record behaviours during the same observation, using the same behavioural categories. They then test the correlation between each tally of behaviour to identify if the behavioural categories are appropriately operationalised.
• Assessing external reliability - Test-retest:

  • Repeating the study using the same procedures at different times with the same participants and test the correlation.