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-Rizhiy- t1_j018jx5 wrote

Reply to comment by SherbertTiny2366 in [Discussion] Amazon's AutoML vs. open source statistical methods by fedegarzar

Do you by any chance have a resource that explains that a bit more?

I can't get my head around how a collection of accurate forecasts, can produce an inaccurate aggregate.

Is it related to class imbalances or perhaps something like Simpson's paradox?

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SherbertTiny2366 t1_j01t4du wrote

Imagine this toy example. You have 5 series, which are very sparse, as is often the case in retail. For example, series 1 has sales on Mondays and 0's the rest of the days, series 2 on Tuesdays, series 3 on Wednesdays, and so on. For those individual series, a value close to 0 would be more or less accurate, however, when you add all the predictions up, the value will be way below the true value.

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