======What models are for?======

  * As basis of understanding

[[https://en.wikipedia.org/wiki/William_Thomson,_1st_Baron_Kelvin|Lord Kelvin]] in [[https://books.google.com/books?id=XWQSAAAAIAAJ|Baltimore Lectures on Molecular Dynamics and The Wave Theory of Light]]
> I am never content until I have constructed a mechanical model of the subject I am studying. If I succeed in making one, I understand; otherwise I do not.

  * Prediction
  * Testing of hypothesis

Model describes a way the data are generated.

Model are usually [[notes:parametric_test|parametrized]].