At 07:15 AM 6/11/2007, Matt Williams wrote:
I changed the subject line to make it more specific.
I think that Evidence is a tricky, slippery subject. It seems to be
both traces (i.e. records of something) and in many cases,
inferences. Those inferences probably shouldn't be called evidence,
but they are the reason that some data are considered evidence, and
others not, and hence often get included.
Actually, sometimes the interpretation *is* part of the
evidence--best example is medical imaging wherein the radiologist
interpretation of the images are part of the primary evidence (the
image is the "raw" evidence, but you have no result without the
radiology interpretation of the image).
Interpretation also transforms raw data into recoded variables that
is also used as evidence, for example in interpreting raw EKG
tracings to give the label of "ventricular tachycardia" or recording
a sodium of 150 as "high sodium."
To take the radiology example below
So evidence is a function of the facts, the
analysis method, the method of inference, and perhaps even the
observer (e.g., if the evidence is a radiology image or physical
exam, there is inter-observer variation).
And it's definitely necessary to relate the hypotheses to the
evidence with probabilities
I would suggest that the interpretation of the evidence is a
function of the facts (plus other things). However, the facts are
not stable (e.g. with a physical examination) and may conflict with
each other; therefore inconsistency is not a just a matter of which
inference procedure you choose, it is also a matter of which facts
(your premises) you start from.
It is also not "definitely necessary to relate hypotheses to
evidence with probability" (although it may be useful). There are a
load of other techniques that don't use probability: e.g. Wigmore
Charts (from 1930's onwards) and more recently, non-monotonic
logical techniques.
I suggested the importance of probabilities because of their utility
in the biomedical domain. Have the other methods you cite been used
in biomedicine? If so, I'd be very interested in looking at the citations.
For a good intro. I would recommend David's Schum's book "The
Evidential Foundations of Probabilistic Reasoning". Also,a look at
the evidence science website might be good: http://www.evidencescience.org/
Thanks for the pointers.
Daniel
HTH,
Matt
