thomblake comments on Raising the forecasting waterline (part 1) - Less Wrong

32 Post author: Morendil 09 October 2012 03:49PM

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Comment author: thomblake 09 October 2012 08:37:09PM 5 points [-]

Talking about increments of 5% runs counter to my intuitions regarding good thinking about probability estimates. For most purposes, the difference between 90% and 95% is significantly larger than the difference between 50% and 55%. Think in logs.

Comment author: Morendil 09 October 2012 09:30:19PM 4 points [-]

Yes, near the extremes it makes a difference - but we're using a Brier scoring rule, averaged over all days a forecast is open. That makes thinking in logs less important - 99% isn't much worse than 100% on errors. I'll discuss that in pt.2 under 'loss function'.

Comment author: thomblake 10 October 2012 01:49:12PM 0 points [-]

I'll discuss that in pt.2 under 'loss function'.

Hooray!

Comment author: [deleted] 10 October 2012 09:30:44AM 1 point [-]

It depends on whether you're using probabilities epistemically or instrumentally. Changing the probability of A from 90% to 95% doesn't affect your expected utility any more than changing it from 50% to 55%.

Comment author: roystgnr 12 October 2012 08:00:15AM 2 points [-]

The change in expected utility given constant decisions is the same for any 5% change in probability regardless of where the baseline is for the change. However, that "given constant decisions" criterion may be less likely to hold for a change from 90-95% than it is for a change from 50-55%. If you have to choose whether to risk a negative consequence of not-A in exchange for some benefit, for example, then it matters whether the expected negative utility of not-A just fell by a tenth or by half.

Comment author: thomblake 10 October 2012 01:49:36PM 1 point [-]

Yeah, that's why I said "For most purposes".