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gverhoev 08-10-2021 11:51 AM

Does a test set exist?
In his recent lecture on testing and validation, Professor Magdon-Ismail said that a test said is used in a fictitious world. Does that mean that the term/concept "test set" does in reality not exist, as one always splits a data set in training and validation sets? And as soon as data are split, they influence the final hypothesis g because there are fewer data points to train. So can one even use the concept of a test set? Or is there a rule when one could use the term test set, also in a real-world situation? Many thanks for your insights!

htlin 08-11-2021 03:36 AM

Re: Does a test set exist?
In my experience, a one-use-only test set usually does not exist in the real applications, given that "one-use-only" is arguably too luxurious in any application. When multiple tests are conducted on the same test set, the set becomes closer to a "validation" set than a test set. But anyway, IMHO those are just naming issues. The important thing is to know that every use on a set can cause some sort of "contamination."

Hope this helps.

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