statistical infrequency

• defining abnormality in terms of statistics

  • the most obvious way to define anything as 'normal' or 'abnormal' is in terms of the number of times it is observed
  • statistics = about analysing numbers
• behaviour that is rarely seen is abnormal

  • 'normal' behaviour = can be seen as any relatively 'usual', or often seen, behaviour
  • 'abnormal' behaviour = any behaviour that is different or rare (statistically infrequent)
• example = IQ and intellectual disability disorder

  • IQ is normally distributed
  • the average IQ is 100 = most people have an IQ between 85 and 115 (only 2% have a score below 70)
  • those individuals scoring below 70 are statistically unusual or 'abnormal' and are diagnosed with intellectual disability disorder
• strength = RWA

  • statistical infrequency is useful in diagnosis:
  • eg intellectual disability disorder because this requires an IQ in the bottom 2%
  • also helpful in assessing a range of conditions:
  • eg the BDI assessing depression = only 5% of people score 30+ (severe depression)
  • means that statistical infrequency is useful in diagnostic and assessment processes
• limitation = unusual characteristics can be positive

  • if very few people display the characteristic = then the behaviour is statistically infrequent but doesn't mean we would call them abnormal
  • IQ scores above 130 are just as unusual as those below 70, but not regarded as undesirable or needing treatment
  • means that although statistical infrequency can be part of defining abnormality, it can never be its sole basis
• extra evaluation = benefits vs problems

  • when someone is living a happy and fulfilled life, there is no benefit to them being labelled as abnormal
  • HOWEVER = the level of abnormality (eg intellectual disability disorder) might carry a social stigma
  • this means that labelling someone abnormal just because they are statistically unusual is likely to do more harm than good