How the Halo Effect turns uncertainty into false certainty




…we tend to turn the volume down on the things that are difficult…

Do you mean like listening to a podcast instead of reading a research paper?


Like, rich people ascribe their wealth to greater virtue and effort? and poor people to lack of said qualities?

Statistically speaking, it is more likely the applicant is a lawyer.

No, no, no! Dead wrong! That is only true if the person was chosen at random, and you did not state that!

If you choose one of the hundred people at random, and don’t say anything about them, then the probability of it being a lawyer are 70%. If you don’t choose at random, probability doesn’t apply. And if you give us information about the chosen person that is correlated with their profession, that changes the odds. Within this sample, is there a positive correlation between being an engineer and being good at math? A negative one between being a lawyer and hating public speaking? Then the variables are not independent, and the straightforward 70% probability no longer applies.


Yeah, it becomes virtually impossible to put a %age number on things if it’s not picked at random, regardless of the other correlations. It could be that, say (to use a ridiculous correlation that is in no way true), 95% of lawyers had type A blood and 95% of engineers had type B, but the person telling you “This guy has type B blood,” you don’t know their agenda. Maybe they’re specifically picking the one lawyer in the group that has type B blood, just so that if you guess based on odds, you’ll guess wrong. Or maybe they’re trying to make a point about how “guessing the most likely scenario” gives you the most likely chance of success, and they picked an engineer with type B blood. Unless you can place a number on the probability of how/why they choose their exemplar, you’re in the dark just as much as if you didn’t know the relative numbers of engineers/lawyers in the first place.


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