Are Levy and Peart the pair who have been smearing the Galtonians for years? Jeez, you’d think they would have something better to do with their time…

Galton was 85 years old when he did the guess-the-weight study and realized that his preconception was completely wrong. So, rather than forget about it and take a nap, he reported his new finding to Nature, which became the starting point for the “Wisdom of Crowds” school of thought that James S. wrote about.

Galton was a great scientist and a great man.

For a less tendentious assessment of Galton’s many achievements (and fewer, but still real, shortcomings), see Jim Holt’s article in The New Yorker:

http://www.newyorker.com/archive/2005/01/24/050124crbo_books

Levy and Peart need to do some soul-searching about why they are so biased against the Galtonians.

I have had time to reflect and now I
would like to offer a more detailed personal apology than what we’ve jointly posted before. When I failed to find Galton’s mean, in spite of your sufficient directions, I should have asked you directly for help. From these two failures of mine, and because Sandy trusted my work, we were led to the wrong conclusion that your account of Galton’s mean was false instead of the right conclusion that your account was simply different than our accounts of Galton’s median. If the
accounts are merely different then we have many ways of asking which of the two estimators one might prefer. We began that helpful exercise. We did not stop there. When we said that your account was false, and asked a rhetorical question of how this came to be, we called into question my own intentions. We also wrongly called into question the care which scholars took in citing your work.

For all this, again, I offer a personal apology.

Best wishes,

David

http://adamsmithlives.blogs.com/thoughts/2007/10/experts-and-i-1.html

One paragraph which will go into the next version is this:

One of Galton’s defenses for the sample median as the vox populi was it that bounds the influence of any individual voter. Replication and checking of the work of experts may be a way to bound the influence of experts. It is important for reader to know that in an earlier version we denied the existence of Galton’s mean. This emphasizes the importance of replication and competition precisely to bound the influence of such error

Here’s what we are prepared to defend :

The majority-rule context of Galton’s publications is lost when the sample median, upon which Galton put such stress, is no longer reported

David Levy

Robin writes: “it is ironic that Galton made quite an effort to emphasize and prefer the median, in part because the data did not look like a bell curve, while your retelling focuses on him calculating a mean after checking for a bell curve.” What’s ironic about this? He did check for a bell curve, and he did calculate the mean. It’s the data themselves, not Galton’s interpretation of them, that I was writing about. (If he hadn’t calculated the mean, I would have happily told the story with the median, since it was also remarkably accurate, and demonstrated the same point about the wisdom of crowds.)

Finally, on the substantive question, Robin (and Levy and Peart) seem to think that because the distribution of guesses wasn’t normal, that makes using the mean a mistake. But this is precisely what’s so interesting: if the group is large enough, even if the distribution isn’t normal, the mean of a group’s guesses is nonetheless often exceptionally good.

In my book, I reference Surowiecki’s “guess-the-weight-of-an-ox” anecdote. My colleague David Levy and his co-author Sandra Peart show that isn’t…