In a related development, this sentence appeared on Geoff Hill's site in September '06:
Through July 2006, nine of fourteen visitors who spent more than 48 hours at the site detected Ivory-billed Woodpeckers.
Monday, June 04, 2007
Observer bias comment thread
I just stumbled onto this August '06 comment thread on John Trapp's blog.
In a related development, this sentence appeared on Geoff Hill's site in September '06:
In a related development, this sentence appeared on Geoff Hill's site in September '06:
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3 comments:
Yes, Tom, I tangled with Bill Pulliam on his use of statistics to try to show that so many supposed "sightings" could not all be wrong.
But of course, not only can they be wrong. They are wrong.
Impartial observers are almost impossible for IBWO researchers to find. They instead have to settle for volunteers who are largely TB's. They are largely young and in awe of the supposed experts. Or older TB's who want desperately to see an IBWO. This adds in a huge amount of Observer Expectancy Bias.
As I and you and others have pointed out, when the CLO started insisting that researchers go into the field in pairs the number of sightings vanished to zero.
It's hard to have two field researchers misidentify a Pilieated as an Ivory-billed at the same time. Not impossible. But you would expect the number of bogus sightings to go down. And it did when the CLO instituted it's "only in pairs" rule.
With your permission Tom, I would like to reprint below my 8 points about Observer Expectancy Bias.
So to sum up. Here is the devastating effect of the Observer Bias argument.
1.people are not robotic automatons that have set error rates during observations.
2.instead their rate of error is influenced by human factors.
3.they change with time due to wishes and wants and their own expectations.
4.these expectations, wants, and wishes are admitted to in various books, lectures, letters and published articles. They “grew up” wishing to see the bird, “dreamed” of seeing it, searched many years, talked to like minded people who shared their desires, and they wish to be recognized in their field of ornithology or birding. (ambition is not bad, just it’s influences)
5.No double blind studies of IBWO sightings is possible.
6.To minimize observer bias, multiple persons per team would be expected to reduce not increase sightings if the bird is extinct.
7.To minimize observer bias, impartial observers would be a plus. But nearly impossible to get all impartial observers on a team. What would that even mean?
8.Observer Bias predicts all that we have seen. Initial sightings, followed by declining sightings. Ultimately producing no real documentation or proof.
It is then, after observer bias has produced erroneous sightings, that Tom's "The Road to Fraud" kicks in. And keeps the whole fiasco going for much longer than reasoned men or women would ever expect.
http://tomnelson.blogspot.com/2006/03/road-to-fraud.html
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