Research Methods: Reliability

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Research Methods: Reliability


  • Refers to consistency of a particular measurement.
  • Researchers should be able to measure/test something time after time and get similar results.
  • Reliability linked to replicability - ability to repeat a study, which is one of the major features of science.

Types of Reliability

A) External Reliabilityability to produce the same results every time. E.g if same person takes a questionnaire/test at two different times and produces same results, the quesitonnaire/test is reliable.

  • Assessing external reliability - external reliability can be checked using the test-retest method. This is where the test/questionnaire is used twice on same ppts. To get a measure of reliability correlate the two scores, the higher the correlation, the more reliable the test/questionnaire.

B) Inter-rater/inter-observer reliability (form of external validity) - concerns whether two interviewers/observers can produce the same outcome and are consistent. The extent to which observers/interviewers agree is known as inter-rater or inter observer reliability.

  • Assessing inter-rater reliability -  inter-rater reliability can be assessed by correlating the scores of the two observers/interviewers/markers scores to give an indication of reliability. The higher the correlation, the more reliable the observations.

C) Internal reliability - concerned with the


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