A phobia is an irrational fear which interferes with daily life. For a phobia to be diagnosed it must meet the criterion set by the diagnostic and statistical manual of mental disorders. Reliability and validity are two important factors when considering classification of mental disorders; they must be present for an accurate classification to be made. Reliability and validity are linked because a diagnosis that is not reliable is not valid.
Reliability refers to the consistency, such as questionnaires or scales to assess how fearful a person is about something. Reliability of questionnaires or scales can be measured in terms of whether the test items are consistent, which is called test-retest reliability. Another way of assessing reliability is whether two independent assessors give similar scores, which is called inter-rater reliability. Test re-test refers to how consistent results are when the specific interview/questionnaire is repeated.
Brown et al (2001) conducted a study which involved interviewing 1400 patients twice, the second interview occurred within 2 weeks of the first one. The interviews were based on criteria for various disorders in DSM –IV. Brown found that reliability in inter-rater agreement was excellent for specific phobia, social phobia and panic disorder wit agoraphobia. Reliability could have been higher for the various phobias than for other mental disorders because all phobias are associated with clear behavioural symptoms (avoidance of feared stimulus) which makes them easy to diagnose. This suggests that diagnosis of phobic disorders according to the DSM is reliable however largely because phobic disorders are easy to diagnose .Brown et al also examined factors associated with disagreement between 2 interviewers. He found that inter-rater unreliability was caused by interviewers disagreeing whether the