(Image: Zen Buddha Silence by Marilyn Barbone.)
December 11, 2016
CLINICAL VS. MECHANICAL PREDICTION: A META-ANALYSIS
William Grove, David Zald, Boyd Lebow, Beth Snitz, and Chad Nelson did a meta-analysis (a study of studies) of 136 different studies of human experts vs. simple quant models. Here is a link to the paper by Grove et al. (2000): http://datacolada.org/wp-content/uploads/2014/01/Grove-et-al.-2000.pdf
Here is what Grove et al. discovered about 136 different studies:
- 64 clearly favored the model
- 64 showed approximately the same result between the model and human judgment
- 8 found in favor of human judgment
(NOTE: All eight cases where human judgment prevailed had one thing in common: the humans had more information than the quant models.)
Across all 136 studies that Grove et al. examined, experts were correct in 66.5% of the cases, while the quant models did significantly better with an average hit ratio of 73.2%.
Paul Meehl, one of the founding fathers of the importance of quant models versus human judgments, had this to say:
There is no controversy in social science which shows such a large body of qualitatively diverse studies coming out so uniformly in the same direction as this one… predicting everything from the outcomes of football games to the diagnosis of liver disease. And when you can hardly come up with a half a dozen studies showing even a weak tendency in favor of the clinician, it is time to draw a practical conclusion.
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There are roughly 10-20 positions in the portfolio. The size of each position is determined by its rank. Typically the largest position is 15-20% (at cost), while the average position is 8-10% (at cost). Positions are held for 3 to 5 years unless a stock approaches intrinsic value sooner or an error has been discovered.
The goal of the Boole Microcap Fund is to outperform the Russell Microcap Index over time, net of fees. The Boole Fund has low fees.
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