Statistical infrequency

• One definition of abnormality is statistical infrequency. This occurs when an individual has a less common and numerically rare characteristic, that is different from the general population. These individuals fall outside the normal distribution (the average in that population) and are located two standard deviations away from the mean and so are considered to be abnormal. An example of statistical infrequency is IQ. For example,the average IQ is set at100.
• The majority of the population (68% of people) have an 1Q range from 85-115, which is the normal distribution. Only 2% of people have a score below 70. Therefore using the definition these individuals scoring below 70 would be considered to be abnormal and therefore are liable to receive a diagnosis of a psychological disorder - intellectual disability disorder (mental retardation).
• There are many strengths of using statistical deviation to define abnormality from its real world application. For example it can be used in the diagnosis of intellectual disability disorder. One way of doing this is performing an assessment of patients with mental disorders including some kind of measurement of the severity of symptoms compared to statistical norms. This clearly supports the definition being a strong explanation for abnormality as it can be applied usefully to the different situations to aid in clinical assessments.
• Continuing strength: real world application Therefore this supports the definition as it shows that it is externally valid.
• However, a limitation of using statistical deviation to define abnormality, is that when someone is living a happy and fulfilled life, there is no benefit in them being labelled as abnormal, regardless of their potential unusual behaviour. For example, someone with a very low IQ but who is not in distress and is quite capable of work would not need a diagnosis of intellectual disability. If that person is labelled as abnormal, it could have a negative effect on their self-esteem.
• Continuing weakness: no benefit of them being labelled as abnormal. This clearly is an ethical weakness of the definition as it could subject someone to unnecessary psychological harm. Thus a cost-benefit analysis should be applied before using it to define someone as abnormal as it could otherwise be detrimental towards society.
• the statistical infrequency definition offers an objective approach to diagnosing abnormality. For example, the definition introduces an element of objectivity into the process of defining abnormality so that different mental health care workers can all view the same kind of behaviour in the same kind of way. This is a strength because it means that no value judgements are made, and that identification of abnormality is free from bias and not affected by the experience and/or opinions of those diagnosing it - meaning they are less prone to abuse
• Unusual characteristics can be positiveIQ scores over 130 are just as abnormal as IQ scores under 70 but no ones see super intelligence as undesirable. Just because some people have characteristics that are abnormal does not always mean that they require treatment to make the 'normal'. This therefore means that this is a limitation of statistical infrequency as it can not be used for diagnosis alone