gwern comments on Open Thread, April 27-May 4, 2014 - Less Wrong

0 Post author: NancyLebovitz 27 April 2014 08:34PM

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Comment author: gwern 29 April 2014 11:31:00PM *  2 points [-]

More importantly, you don't seem to dispute that your calculation doesn't really address my claim.

I did dispute that:

My calculation addresses a major part of the Bayesian calculation...that sharply limits how much could ever be inferred from observing [Roberts] dying.

(A simple countermeasure to avoid biasing yourself with anecdotes: spend time reading in proportion to sample size. So you're allowed to spend 10 minutes reading about Roberts's 1 death if you then spend 17 hours repeatedly re-reading a study on how fat consumption did not predict increased mortality in a sample of 100 men.)

Comment author: brazil84 30 April 2014 01:05:17AM 1 point [-]

I did dispute that:

My calculation addresses a major part of the Bayesian calculation...that sharply limits how much could ever be inferred from observing [Roberts] dying.

I wouldn't call it "major" because (1) you refuse to assign a probability to an event I stated I thought was likely; and (2) the main point of your calculation was pretty non-controversial and even without a calculation I doubt anyone would seriously dispute it.

Let's do this: Is there anything I stated with which you disagree? If so, please quote it. TIA.

Comment author: gwern 30 April 2014 01:23:53AM *  -1 points [-]

I wouldn't call it "major" because (1) you refuse to assign a probability to an event I stated I thought was likely;

It puts an upper bound as I said. Plug the specific conditional I calculated into Bayes theorem and see what happens. Or look at a special case: suppose conditional on the diet not being harmful, Roberts had a 50% chance of dying before 80; now, what is the maximal amount in terms of odds or decibels or whatever that you could ever update your prior upon observing Roberts's death assuming the worsened diet risk is >50%? Is this a large effect size? Or small?

(Now take into account everything you know about correlations, selection effects, the plausibility of the underlying claims about diet, what is known about Roberts's health, how likely you are to hear about deaths of diet gurus, etc...)

(2) the main point of your calculation was pretty non-controversial and even without a calculation I doubt anyone would seriously dispute it.

One would think so.

Comment author: brazil84 30 April 2014 07:42:02AM 0 points [-]

It puts an upper bound as I said.

So what? One can trivially put an upper and lower bound on any probability: No probability can exceed 1 or be lower than 0. But it ain't "major" to say so. On the contrary, it's trivial.

Anyway, please answer my question: Was there anything in my original post with which you disagreed? If so, please quote it. TIA.

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