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Judgement (The conjunction fallacy (too many options? (gave 142 people a…

- - - - 50% of staff & students at Harvard Medical School estimated the probability at 95%. This is known as ‘base rate neglect’. Only 11/60 answered 2%, which is correct.
  - - - Input information changed from percentages to frequencies eg "out of every 1000 people who are perfectly healthy, 50 of them test positive for the disease (i.e., the "false positive" rate is 5%)"
        
        correct answer rate increases from 12% to 56%, base rate neglect decreases from 56% to 4%
- - - - however no single conception of probability is shared by all statisticians and philosophers
      - blindness to content and context
      - makes unrealistic demands of the mind - problem space is unabounded
- - - - If you pick a word (over three letters long) at random from an English text, is it more likely that the word starts with an ‘r’ or has ‘r’ as its third letter? Most participants said ‘starts with r’ was more likely. Actually, many more words have ‘r’ as their third letter, but these are harder to bring to mind.
    - - If you pick 2000 words at random from a novel, will there be more words ending ‘ing’ or more words ending ‘n’? Most said ‘ing’ which must be wrong!
    - - Asked participants to judge which was the most likely of two causes of death
      - For example, is it more likely that someone will die in a tornado or from asthma
      - Identified “many, often severe, misconceptions
      - 58% of student sample thought tornado was more likely (actually asthma 20x more likely)
    - - Newspaper reports overrepresented more ‘dramatic’ causes of death (disasters, accidents, homicide etc.)
      - People’s risk judgements were related to frequency of media coverage
      - More evidence for use of an availability heuristic
    - - Diseases with high media presence (e.g. avian
        flu) judged more severe than other diseases
    - - But availability can also be affected by internal, psychological factors. For example, positive and negative information is recalled more in the appropriate mood. So if you’re in a good mood, you are more likely to recall positive things, and if you’re in a bad mood, you’re more likely to recall negative things. This is especially true in conditions like depression. Therefore the availability of information is not constant, it varies as a function of other psychological factors. This could be a problem in conditions like depression where people will overestimate the probability of negative evens occurring.
  - - - Group 1
        
        Is % of African countries in UN < > 10%? OR estimate product of 8 x 7 x 6 x 5 x 4 x 3 x 2 x 1
        
        Now estimate number of countries : 24% OR 2250
      - Group 2
        
        Is % of African countries in UN < > 65%? OR estimate product of 1 x 2 x 3 x 4 x 5 x 6 x 7 x 8
        
        Now estimate number of countries : 45% OR 512
      - demonstrates differences in estimates based on phrasing of Q # #