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 is about analyzing numbers
• Behavior that is rarely seen is abnormal:

  • Any relatively 'usual', or often seen, behavior can be thought of as 'normal'
  • Any behavior that is different, or rare, is 'abnormal', i.e. a statistical infrequency
• 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 bellow 70 are statistically unusual or 'abnormal' and are diagnosed with intellectual disability disorder
• One strength of statistical infrequency is its real-world application

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

  • Every few people display a characteristic, then the behavior 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 undesireable or needing treatment
  • This means that although statistical infrequency can be part of defining abnormality, it can never be its sole basis
• Evaluation extra: Benefits vs problems

  • When someone is living a happy and fulfilled life, there is no benefit to them being labelled as abnormal
  • However the label of abnormality, e.g. 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