24 DEC 2013 by ideonexus
Predictability and the Base Rate
Whenever a statistician wants to predict the likelihood of some event based on the available evidence, there are two main sources of information that have to be taken into account: (1) the evidence itself, for which a reliability figure has to be calculated; and (2) the likelihood of the event calculated purely in terms of relative incidence. The second figure here is the base rate. Since it is just a number, obtained by the seemingly dull process of counting, it frequently gets overlooked wh...Folksonomies: predictability
Folksonomies: predictability
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notes
notesKeith Devlin explains why the accuracy of tests and measurments must take into account the base rate for the phenomenon.
13 APR 2013 by ideonexus
The Problem with Occam's Razor
In climate forecasting, the situation is more equivocal: the theory about the greenhouse effect is strong, which supports more complicated models. However, temperature data is very noisy, which argues against them. Which consideration wins out? We can address this question empirically, by evaluating the success and failure of different predictive approaches in climate science. What matters most, as always, is how well the predictions do in the real world.
I would urge caution against reducin...
1 Not all models can be simple.
13 APR 2013 by ideonexus
Bayes' Theorem Means Scientific Consensus Should Converge
One property of Bayes’s theorem, in fact, is that our beliefs should converge toward one another—and toward the truth—as we are presented with more evidence over time. In figure 8-8, I’ve worked out an example wherein three investors are trying to determine whether they are in a bull market or a bear market. They start out with very different beliefs about this—one of them is optimistic, and believes there’s a 90 percent chance of a bull market from the outset, while another one i... 1 notes
notesAs more and more tests are carried out, scientific opinions should converge around the truth.
12 APR 2013 by ideonexus
Prediction VS Forecast
The official position of the USGS is even more emphatic: earthquakes cannot be predicted. “Neither the USGS nor Caltech nor any other scientists have ever predicted a major earthquake,” the organization’s Web site asserts.24 “They do not know how, and they do not expect to know how any time in the foreseeable future.”
Earthquakes cannot be predicted? This is a book about prediction, not a book that makes predictions, but I’m willing to stick my neck out: I predict that there will... 1 notes
notesOne is a definitive statement, the other a probabilistic one.
21 SEP 2011 by ideonexus
Are Humans Still Evolving?
Anybody who teaches human evolution is inevitably asked: Are we
still evolving? The examples of lactose tolerance and duplication of the
amylase gene show that selection has certainly acted within the last few
thousand years. But what about right now? It’s hard to give a good
answer. Certainly many types of selection that challenged our ancestors
no longer apply: improvements in nutrition, sanitation, and medical
care have done away with many diseases and conditions that killed our
ancestor... 1 notes
notesCulture has removed many of the selective pressures from human survival, allowing harmful mutations to build up in the genepool; meanwhile, people living in third-world countries continue to experience selective pressures from droughts, famines, and disease.
