- Suppose one forecaster says the probability Trump wins is q and the other says the probability is p>q. If Trump in fact wins, who was “right?”
- Suppose one forecaster says the probability is q and the other says the probability is 100%. If Trump in fact wins, who was right?
- Suppose one forecaster said q in July and then revised to p in October. The other said q’ < q in July but then also revised to p in October. Who was right?
- Suppose one forecaster continually revised their probabilistic forecast then ultimately settled on p<1. The other forecaster steadfastly insisted the probability was 1 from beginning to end. Trump wins. Who was right?
- Suppose one forecaster’s probability estimates follow a martingale (as the laws of probability say that a true probability must do) and settles on a forecast of q. The other forecaster‘s “probability estimates” have a predictable trend and eventually settles on a forecast of q’>q. Trump wins. Who was right?
- Suppose there are infinitely many forecasters so that for every possible sequence of events there is at least one forecaster who predicted it with certainty. Is that forecaster right?
Cheap Talk
A blog about economics, politics and the random interests of forty-something professors
Cheap Talk 
4 comments
Comments feed for this article
August 4, 2016 at 12:51 am
Enrique Guerra-Pujol
In other words, how many pollsters use sound statistical methods (random samples, unbiased questions, etc.) and how many are hucksters?
October 7, 2016 at 2:43 pm
C
I don’t think that is the point. The problem is that you have only one realization of a random process. There is no way to make inferences from one realization.
The “true” probability (if that exists) of Trump winning might be 1e-6; unlikely to occur but it could still happen. If it does is someone predicting a Trump win w.p. 1 correct? Knowing the true probability we would say “no”. However, for these unique events we never see/can estimate the true probability.
November 6, 2016 at 12:43 pm
João rodarte
João rodarte
Thoughts Left Lying Around About Election Forecasts | Cheap Talk
October 11, 2017 at 3:16 am
graphics313
Man with a Van Service
Hire Man with a Van, House Clearance, Furniture & House Moving Service. Home Temovals in London, Sussex, Surrey, Hampshire, Kent, Liverpool.
for more information please call us 0800 0 119
http//www.deliveryd2d.com