# Inevitable Illusions

From: Chris De Voir (devoirc@biotronik.com)
Date: Fri Jun 01 2001 - 11:24:40 MET DST

• Next message: Jimi Shanahan: "Extended Deadline: MODELLING WITH WORDS Workshop - FUZZ-IEEE 2001"

Thank you for your comments and clarifications. But there is a particular
slant to my line of questioning that I am trying to convey. I offer another
example found at:
http://www.dcs.qmw.ac.uk/~norman/BBNs/Representativeness.htm (where there
are more examples relevant to thread of my original question).

"Insensitivity to prior probability of outcomes

Suppose you are given the following description of a person:

'He is an extremely athletic looking young man who drives a fast car and has
an attractive blond girlfriend.'

Now answer the following question:

Is the person most likely to be a premiership professional footballer or a
nurse?

If you answered professional footballer then you were sucked into this
particular fallacy. You made the mistake of ignoring the base-rate
frequencies of the different professions simply because the description of
the person better matched the stereotypical image. In fact there are only
400 premiership professional footballers in the UK compared with many
thousands of male nurses, so in the absence of any other information it is
far more likely that the person is a nurse."

In light of this example, the questions I am really trying ask are:

1. Would not Fuzzy thinking yield an answer that would be consistent with
(in the same ballpark as) what Kahneman & Tversky say is the correct answer?

2. What "systeme" in Fuzzy assures this? In another post to this list,
"Bayes-learning-thought etc", Martin Lefley (Thu Jan 18 2001) stated,
"Bayesian reasoning is represented by formulae that could be represented
by...FLS...." Does anyone have a pointer to this method?

3. Could Fuzzy thinkers come up with answers that Kahneman & Tversky would
identify as heuristically biased? This is not a rhetorical question, since
#4 and #5 follow.

4. In that case, what essential(s) of the Fuzzy reasoning process has been
overlooked or misapplied?

5. In the case of #3 as an outcome, could it be that no violations Fuzzy
reasoning have occurred?

Chris.

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