
AI Predicts Obesity Prevalence from Space - imartin2k
https://singularityhub.com/2018/09/17/this-ai-predicts-obesity-prevalence-all-the-way-from-space/
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tlb
Paper at
[https://jamanetwork.com/journals/jamanetworkopen/fullarticle...](https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2698635)

This paper abuses cross-validation to claim an unreasonably high accuracy.

They trained their model on census tracts from 6 US cities, and tested it with
5-fold cross-validation. That means you split the data randomly into 5 groups,
and train with 4/5 and validate with the other 1/5.

Suppose, for the sake of argument, that census tracts come in groups that are
basically identical, because they're built by the same subdivision builder and
moved into at the same time, and are served by the same grocery stores and
restaurants and schools, and they have similar incidences of obesity. (In US
suburbia, a census tract is typically 1 block with ~30 inhabitants.)

A random leave-1/5-out cross validation can report high accuracy, even with a
highly overfitted network that just memorized the tracts it saw. Because the
5-fold validation still preserves at least one member from every group of
identical tracts.

It'd be more impressive if it could predict obesity for a city it hadn't seen.

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jmpman
Can it also predict wealth? Aren’t obesity and wealth correlated? Suspect
green lawns and widely separated houses predict wealth compared to mobile
homes in a barren lot packed together.

