statistical infrequency

• statistical infrequency:

  • mathematical method for defining abnormality
  • abnormality should be based on infrequency; if behaviour occurs rarely then its abnormal
• mathematical idea around statistical infrequency:

  • the idea that human attributes fall into a normal distribution within the population (e.g height & weight)
  • this means that there is a central average (mean) and the rest of the population fall symmetrically above & below that mean
  • standard deviation as a measure informs us how far scores fall on either side away from the mean
• what is standard deviation?

  measure of the spread of data
• what are the percentages on the normal distribution graph?

  green = 34.1%

  blue = 13.6%

  purple = 2.1%

  
• what does the +1SD and the -1SD stand for on the graph?

  how many standard deviations they are away from the mean e.g if you are in the 2.1% on the right of the graph, that means you are +2 standard deviations away

  
• IQ test scores:

  it is calculated based on a norm group with an average score of 100 and a standard deviation of 15

  • a standard deviation of 15 means 68% of the norm group has scored between 85 (100-15) and 115 (100+15) so 68% of the norm group has a score within one standard deviation
• normal distribution of IQ:

  • the behaviour occupies the extreme ends of a normal distribution curve
  • a low IQ is defined as intellectual disability disorder
  • IQ relies on up-to-date statistics
  • scoring between 70-130 is considered a normal IQ
  • an IQ less than 70 or more than 130 is statistically infrequent and considered abnormal
• what are the issues with abnormality and IQ?

  when someone has an abnormally high IQ they are not seen as abnormal or negative, they are termed as genuius
• what percentage of the graph determines someone as abnormal?

  the 2.1%

  
• what do you need to have in order to be diagnosed with Intellectual disability disorder:

  a low IQ

  some of Rosehan and Seliman’s features (failure to function adequately)
• give an example of behavior that occupies the extreme ends of the normal distribution curve:

  intellectual disability disorder
• evaluation points for statistical infrequency:

  • real-world application
  • objective
  • unusual characteristics aren’t always undesirable