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opyate (1) [Avatar] Offline
Version 9 states on page 14:

A parametric model is characterized by having a fixed number of parameters whereas a non-parametric model's number of parameters is infinite (determined by data).

As an example, let's say the problem was to fit a square peg into the correct (square) hole. Some humans (such as babies) just jam it into all the holes until it fits somewhere (parametric). A teenager, however, might just count the number of sides (4) and then search for the hole with an equal number (non-parametric).

Why is the teenage example called non-parametric when it has a known number of sides (4), which sounds to me like parametric's "fixed number of parameters"?

Could this be explained a bit better? Another analogy, maybe?