Statistical infrequency evaluation

• Application to the real world

  One strength of statistical infrequency is its usefulness.

  Statistical infrequency is used in clinical practice, both as part of formal diagnosis and as a way to assess the severity of an individual's symptoms. For example a diagnosis of intellectual disability disorder requires an IQ of below 70 (bottom 2%). An example of statistical infrequency used in an assessment tool is the Beck depression inventory (BDI). A score of 30+ (top 5% of respondents) is widely interpreted as indicating severe depression. This shows that the value of the statistical infrequency criterion is useful in diagnostic and assessment processes. Unusual characteristics can be positive
• Some characteristics positive

  One limitation of statistical infrequency is that infrequent characteristics can be positive as well as negative. For every person with an IQ below 70 there is another with an IQ above 130. Yet we would not think of someone as abnormal for having a high IQ. Similarly, we would not think of someone with a very low depression score on the BDI as abnormal. These examples show that being unusual or at one end of a psychological spectrum does not necessarily make someone abnormal.

  This means that, although statistical infrequency can form part of assessment and diagnostic procedures, it is never sufficient as the sole basis for defining abnormality.
• They need a label?

  Some unusual people benefit from being classed as abnormal. For example someone who has a very low IQ and is diagnosed with intellectual disability can then access support services or someone with a very high BDI score is likely to benefit from therapy.

  On the other hand, not all statistically unusual people benefit from labels. Someone with a low IQ who can cope with their chosen lifestyle would not benefit from a label. There is a social stigma attached to such labels