Reliability and validity

• Inter rater reliability:

  • The consistency between two different interviewers.
  • ie. how the two interviewers behave and influence the participant's answers.
• External reliability:

  • A measure of whether something varies from one time to another.
  • ie. is consistent over time
  • ie. test-retest where the same psychological test is given to the same participants on two occasions to see if the same result is obtained.
• Internal reliability:

  • A measure of whether a questionnaire is consistent within itself.
  • ie split- half- method. Test items are split into two halves and the scores on both halves are compared.
  • Scores should be similar if test is reliable
• External validity:

  • Concerns the extent to which the results from a questionnaire or interview can be generalised beyond the particular study.
• External validity (population validity):

  • concerns the extent to which the results of a study can be generalised to other groups of people besides the participants who took part in the study.
• External validity (ecological validity):

  • concerns the ability to generalise a research effect beyond the particular setting which it is demonstrated to other settings.
  • In a questionnaire or interview, the issue is whether responses to questions on a topic actually represent the target behaviour.
• Internal validity:

  • Concerns whether a test (questionnaire) does assess what it intends to assess.
• (Internal validity) Researcher bias:

  • An interviewer has expectations and beliefs which may be unconsciously communicated through to participants.
  • ie tone of voicing or phrasing of a question.