Definitions of abnormality: statistical infrequency
Statistical infrequency defines a behaviour as abnormal when it is rare in the population. Psychologists use statistics to decide where 'normal' ends and 'abnormal' begins.
Real World
An IQ score below 70 falls more than two standard deviations below the mean of 100 and is statistically infrequent, which is why clinical psychologists historically used this cut-off to diagnose intellectual disability.
Exam Focus
State the key limitation: statistical infrequency labels desirable traits like genius IQ as 'abnormal' too.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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