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When the U.S. air force discovered the flaw of averages

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Re: When the U.S. air force discovered the flaw of averages

#51
post #4

Is it just me or does this sound oddly familiar to machine learning recommendation systems? ie: show an item based on the average of all the other items that everyone else has looked at.

Perhaps for a naive recommendation system, but quality ones don't do this.

For example if you employ 1-nearest neighbors, you will actually return a sample that is guaranteed to reproduce another user's preferences. You could of course sample over more neighbors, smoothing results, at the cost of more lookups and at some point in the limit you do see reduced performance due to too many points becoming similar and having this average of everyone being bad for everyone sort of thing. Most ML approaches account for this and will only look at user/item clusters where the assumption is that a user can be sampled from a user cluster and an item can be sampled from an item cluster. Locally you may have error incorrectly capturing the clusters but in practice this works fairly well and you dont have a one size fit all model.

If you're thinking about the cold start problem when you dont have any information about a user, yes it's possible that your overall statistics is a combination of many subpopulations that doesn't really fit anyone very accurately but there are ways around this as well.

So in short - a naive ML recommender that perhaps you get out of a textbook would certainly face these issues but the are addressable in production with an "industry" grade recommender system and will lead to better performance. I don't have firm numbers but in A/B/C tests compared to other black boxes I've seen 20-30% better performance when you start to address some of these issues.

Re: When the U.S. air force discovered the flaw of averages

#53
post #49
post #46

The thing that strikes me here is how much we repeat the mistake of Norma (taking the mythical average body and assuming that differences mean problems) today in talking about people's minds. I started using computers before it was fashionable, before my fellow nerds started being worth billions and ending up on magazine covers. It's hard to describe now how much our difference was seen as wrong, as the sign of a pro…

Modern psychology does not care about average it cares about capable of functioning in society. If you can't avoid say screaming in public that's a problem not just a non issue. Arguably the tolerances might be low, but it's hard to argue with the basic premise. Granted doctors assume if your talking to them you have a problem. But that's arguably a reasonable prior. PS: The extremes of behavior get very far out ther…

>If you can't avoid say screaming in public that's a problem not just a non issue. Arguably the tolerances might be low, but it's hard to argue with the basic premise.

People are prescribed stuff for much much less than "screaming in public", including feeling stressed in BS high stress jobs, being "hyper-active" at school, etc -- with "modern psychology" more often than not siding with the normality of abnormal and abusive societal norms (as it always did. Science is conservative. Not so long ago you got medical treatment for being gay, for example).

>Granted doctors assume if your talking to them you have a problem. But that's arguably a reasonable prior.

Doctors also prescribe and over-prescribe all kinds of BS to people who don't need it, and get all kinds of pharma percs for doing so.

Heck, they'll go even to doing un-needed operations, compared to that, prescribing BS is nothing:

https://www.google.gr/search?q=uneeded+operations+scandal

Re: When the U.S. air force discovered the flaw of averages

#55
post #34

Earlier quoted context omitted.

The simplest example I can come up with is the weight - the density of humans is probably constant for practical purposes and therefore the weight must be positively correlated with your body dimensions. It is also pretty obvious that humans, or tissue for the matter, does not grow in a strongly directional manner. If you gain weight more or less all dimensions not constraint by your skeleton will increase, i.e. you…

Sure, but weight gain in adulthood doesn't cause you to get taller.

That is way I said not constraint by your skeleton - or what ever else. The point is that at least some dimensions are obviously correlated, not that all dimensions have to be correlated.

Re: When the U.S. air force discovered the flaw of averages

#57

Wow! This has implications for human genetics (a study that originated partly in considering human body size measurements like those described in the article) that I think most popular writers on human genetics have not taken into account. There was an article posted to Hacker News earlier this week that suggested, surely falsely in my opinion, that human genomes can be optimized for intelligence to such a degree tha…

Actually if anything this phenomenon would increase the probability of the super IQ thing. Intelligence isn't determined by one gene, but many thousands. Just like there are very few people who happen to be exactly average on dozens of different traits, there are very few people who happen to have the absolute best possible combination of genes to get max intelligence.

That is, assuming there is some optimal combination of genes, it gets exponentially more unlikely any individual has it, the more genes there are that affect intelligence. Just like you would be unlikely to flip 1,000 heads in a row. In fact flipping even 600 heads out of a thousand, is exceedingly unlikely.

Re: When the U.S. air force discovered the flaw of averages

#58

The concept of no members of a group fitting into the average range for all observations is reminiscent of the 'curse of dimensionality'. Can anyone with a data science background make the connection here? Secondly, this seems to explain why everyone hates autocorrect.

Yes, this can be made precise: For example, consider a uniform distribution on a d-dimensional cube with side length 1. Only a (1/2)^d fraction of the mass is within 0.25 distance of the average in every coordinate. In high dimensions, almost all the mass is "near the boundary" in at least one coordinate.

Weirdly enough, even the proportion of points within a distance of 1/2 to the midpoint becomes really small for higher dimensions.

Re: When the U.S. air force discovered the flaw of averages

#59
While hindsight is 20:20, parts of this should have been more obvious.

> Daniels generously defined as someone whose measurements were within the middle 30 per cent of the range of values

> Daniels discovered that if you picked out just three of the ten dimensions of size ... less than 3.5 per cent of pilots would be average sized on all three dimensions.

30% raised to the third power is 2.7%. Basic probability. I guess everyone assumed there would be heavy clustering instead of largely independent variables?

Re: When the U.S. air force discovered the flaw of averages

#60

Articles like this remind me how rational and practical the military is. I know so many brilliant military minds, yet war itself seems outdated and plagued by so many emotionally irrational decisions. I can't reconcile those two thoughts. How can people inside the military be so incredibly smart, yet still think it makes sense to ... you know, kill people's friends and families and not expect them to become terrorist…

I can't speak for the entire military[1], but I've known a few "brilliant military minds" and they rarely, if ever, talk in terms of killing. The military's goals are usually things like area denial, disrupting lines of communication, limiting access to materiel and supplies, degradation of morale, etc. These aren't just euphemisms. If you're trying to win a war solely by killing the enemy, you're going to be in for…

I wouldn't say "raw bloodlust" is accurate. I'd say the life of a serving infantryman is so boring, repetitive, and mundane that getting the chance to use your training in combat will look very pleasing to almost anyone. Especially on deployment.
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